Is this fair?

It's hard to say whether you're taking advantage or she's trying to use you as a slave. But ultimately, if you have no other place to go you may need to buckle down and do want she wants...for now. 

From what you are saying it sounds like you are doing a LOT of unpaid work for your cousin's business, so why is it you are not getting paid - or at the very least, recognition for the amount of work you do? Assuming it is full on and not once in a while you are being asked to help out? 

You forgot to mention that you are spending your days writing fanciful tales to be published on an internet question and answer site.  Obviously you are not even pulling your shadow let alone your weight.  Wasn't that the point of the story?

of course u should be diligently cleaning. what else do u have to do all day? u can't get that many packages to pick up and return, certainly u can find tome to clean in between that activity

I would say you aren’t pulling your fair share of the weight. If you cannot contribute at all financially, then you should be doing essentially everything at the house. Not “help with the cooking”, do all the shopping, planning, prep, cooking and clean up for all meals. Not typically taking laundry initiative or frequently hanging up the wet clothes, but doing all laundry, start to finish, every time. You say nothing of cleaning the bathroom, running the vacuum, or doing anything else beyond occasional dishes or trash. Your contributions of running errands, etc. reads like someone who is trying to dress up a resume. It’s like you want thins to sound bigger and more important than they are-pick up packages, mail out important documents, order and track items? Unless she has a from home business where she is shipping a bunch of stuff and has a ton of packages that for some bizarre reason wouldn’t actually be delivered, this is not something that takes daily time, or maybe even much weekly time, depending on the week.

I think you are ripping her off and getting quite the deal with no financial contribution.

See if you can move out to someone else.

You two need to negotiate a clear cut division of responsibilities. I would literally write it all down and sign off on it like a contract. Then there is no confusion and she can't keep trying to change the terms on the fly. The fact that you don't pay rent doesn't make a difference, you aren't an indentured servant and she can't order you around. 

Managing her mail, bills, and medications isn't work for a roommate. You really should stop doing these things, it's going to be a problem for her in the long run. But if she wants you to continue to be her personal assistant, then you have some leverage to negotiate.     

It doesn't matter what WE think, it only matter how the two of you communicate about this issue. Suggestion: Print out this post, tell her how Yahoo Answers works, and that you posted it to get opinions from people on the internet. Ask her to read it and give you her opinion. Let that be a springboard for a conversation about expectations in the home, and fairness.

I agree.  She is taking clear advantage of you.  Teach her a lesson and move out.