How can you help your horse become more willing and have a stronger work ethic?

The means tags that you try to place on the horse will do nothing for you nor the horse.  I thoroughly read your question, and I have a question for you. Why was she not continued  be allowed as a brood mare? Perhaps you mentioned something about her disposition, and this bring up another question? Has she been examined by a Vet? Her actions seems to show that she might have an internal problem causing pain.  Take her to a Vet and  and learn what is the problem.

The horse is a reflection of you. Nothing to do with it's past. When you start giving a horse labels like "lazy" "stubborn" "dominant" you're setting a horse up to fail. Also you're showing that, while you are obviously a compassionate owner and a decent rider you don't understand the psychology of your horse. You have no idea what her instincts are driving her to think. 

A horse, as you know, is a herd animal. And in that herd there is a hierarchy and there is no equality. You are either higher or lower. If a higher horse asks a lower horse to move, it does so and quickly without protest. A horse that is not sure of it's position or one that ones to challenge it's higher horse with move eventually but under protest. They will swish their tails, pin their ears, kick or maybe even stand their ground and refuse to move. You may notice eventually she becomes "lazy" when not under saddle as well. You haven't proven yourself to be a smarter, stronger leader yet. Maybe that will take more time. My gelding immediately accepted me as a leader and seems to see all humans as above him. Anyone besides me can ride him and he'll behave perfectly. My mare tests me every single day. It's her nature. She accepts me as leader but she must check if she can move up everyday. You may have to accept this is her personality and toughen up a little bit. In the horse world, who ever moves the other's feet is higher. Maybe some ground work would help establish this.

I'm guessing this is a SMART horse.   Am I right?

"Is she just taking advantage of me?"    Not really.  She's just being how horses are with someone they don't respect or trust.    She doesn't think she was put on this Earth to entertain you.

"It seems like because she is lazy she makes work even harder on herself"    You haven't taught her that when she gives you even a BIT of what you ask for, she gets a release which makes her life easier.

IMO your entire philosophy about horses needs to change and you need to back up and start over.

You shouldn't even be riding her if she is constantly bucking/kicking, etc.   You work with her on the ground.   You can do all the basic things from the ground that you can do in the saddle.   You can move her HQ, FQ, laterally, walk, trot, canter, back up, transitions, etc. all from the ground.   You get on ONLY when she is compliant, safe, her head is in the game and she is giving you what you ask.  

You should be forming a partnership with your horse.   You start by asking for the smallest thing and then when you get it, you reward with a release.   And then you build from there.   Learn your phases.   Suggest, ask, tell.    Only use the pressure you need and then release when she gives it to you.

Honestly, anyone who thinks the right way to work with a challenging, defiant, bucking, kicking horse is to get on and try to power through it and that somehow this will magically create a happy, willing, trusting horse is on another planet.

Please find a teacher who can teach you how to work with this horse.     Look into some Natural Horsemanship stuff and start with the groundwork.    This is a 1200 lb animal.  You're NEVER going to win a strength battle.  You have to learn this horse's language and earn her respect in another way.

It takes tons of practice starting and stopping and a huge amount of praise.

I had a halfblood Belgian mare that broke every rule in the book when it vpcame to heat horses could do and couldn’t.  She was noted to be lazy, stubborn and mule like.  When I bought her she was just recovering from a tenderness injury.

I had the mate just over a yews before I discovered she could canter and had a smooth gallop.  She also had a lively extended trot that she would only do for me.

I vent tell you hoe many hours I spent talking to her, hand grazing her and brushing her.  There were times I thought her skin would wear out she was briehrd so much.

The third year I owned her she turned into a beautiful liver dappled coat.  Her fetlocks grew back the hair that burned off from unsanitary conditions where I bought her at.

The trainer tried showing me the proper way to get her to canter, it was always the same, once around the arena and a dead stop.  The teacher. Took the crop to her and slapped her rump silly it had no effect, she did spurs, again no effect.  She got cropped her on the neck and she went... fill out...never saw a 2500 pound horse run that fast ever ever... not only that she refused to stop...ten laps still going strong,  when she finally stopped she grabbed the instructor by the knee and tried yanking her off, when 5hwt didn’t work she tried running once more around the arena (indoor) and tried shaving her off against the wall.

After that I had no problem with Belle, she did everything I wanted and more.  When I Checked her after the instructor tide I saw welts on her butt and neck ad well as dents in her ribs from the Spurs.

My horse hated the lunge line but would go nicely at a walk, trot and jog.   She took a bit to warm up and would let me know by bucking or stopping dead and looking directly back at me with that Well? Expression on her.

We got her just past level 2 dressage.  When we had her vet checked for a show the vet said she read up in her late twenty’s not teens.  She was naturally slowing down  

I worked with her indoors and she went on verbal direction.  She started, stopped, changed gears and direction just by a shift in my body.  Nobody could figure out how I trained her so fast.  I averaged about ten hours a day on her or with her just practicing different things.  I even taught her to stand by tree stumps  or bricks, tailgates end ladders to make it easier for me to get on my 18hh plus wide horse.  It felt as though I was sitting on a Volkswagen bug with a saddle and bridle.

We were learning more advanced moves like jogging in place just to see if she could do it.  She had the most beautiful movement when she wanted to, gorgeous  to watch.  I figured with an old girl like her when I bought her she wouldn’t even be able to run, she dragged her hooves away she plodded along.  After the first year and exercise,lots of love she no longer dragged her feet but walked normally.  You should have seen her vet when she came out of the barn stepping high and prancing tail up and head tucked in.  

You don’t always need a purebred expensive horse to get something fantastic from them.  You do need tons of live, patience and understanding.  Never ever get mad at them for testing you out, your horse will eventually stop her shenanigans once she trusts you more.  When the bond is there she will start workin to please you and will try her best.  It sounds like here still testing the eater with you end had not decided to put in full effort.  I can’t express the talking to your horse, chatter away when riding, briefing, bathing, feeding and talking up.  The more used to your voice she gets the better her will respond to it.

If she's in no pain, she actually has the fitness to comfortably do what you're asking, the behavior isn't tied to her heat cycle, and you're a reasonably skilled rider who is not causing her confusion or discomfort (does she display the same behavior with, for example, your trainer on board?), there may be little you can do besides try to find activities that she actually enjoys (which may not be what you want to do with her). Some horses just don't like to work, or don't like particular types of work.  

My very first horse, decades ago, was similar. He loved beginning riders and leisurely trail rides, but put someone on that knew what they were doing and tried to make him do harder work he didn't want to do, and they would be summarily dumped on the ground. Once I grew in skill and started asking him to work harder and experiencing his vigorous protests, he wound up sold to a dude ranch where he happily plodded along on trail rides as one of their most bombproof mounts until retirement. 

I'd far rather have a horse that is volatile but enthusiastic than a lazy horse with no interest in working with me. The former is fixable; the latter, less so. Plus, riding should be a partnership between you and the horse, not a master/slave relationship. If you have to force your horse to participate, what's the fun in that? Beautiful movement or not, she may just not be the horse for you. 

maybe you can reward him for doing what you want him to do