Snobby sister-in-law- help!?

My husband and I have been having marital problems for a few years, mainly due to his being bipolar manic depressive (and unwilling to take meds or counselling). I have voiced concern to his family (sisters, parents) several times about his issues. His family claim they are very very close, yet his sisters have NOTHING to do with my husband (or our kids), unless it serves them somehow. Anyways, my husband was recently sent on a long business trip, and the day he left, his sisters started sending me emails questioning my commitment to their brother, questioning why I only work 30 hours a week ("Why don't you get a career or REAL JOB like the rest of us?"), why I am selling some furniture (we dont need it!), etc. They also have been saying things like "no wonder you and Chris have issues and stress- you don't DO anything."

I work 30 hours a week, home with the kids while my husband is gone 10 months a year, have two college diplomas, keep a clean house, and generally do my own thing. I don't ask them for help, I don't ask them to be friends. They always send messages to "all the girls in the family" on Facebook, about a shopping trip, movie night, etc- and NEVER ONCE have invited me. They take their kids for professional "the cousins" photos for my parent-in-laws, and never once have they included my children. They often host parties, and I never get an invite. I have never ever done anything nasty to these women. I have an entirely different set of beliefs than they do, but I have never done anything snarky to them.

Once, at my bridal shower, my mother sat down in between my sister in laws- and they BOTH looked horrifed, then got up and moved to another set of chairs (my mother is schizophrenic, and she freaked out my in laws). At the wedding, they flat out refused to do photos with my family. I heard one of them say "talk about wrong side of the tracks!"

I grew up in a poor family, with a schizo mom and absentee father. I never had brand name, I always worked to buy my own items. These ladies have NEVER wanted for anything. My husband and I have always had hard times, due to his mental health issues, and my having to take care of him. My sister in laws always say things like "Well if you're so hard up why don't you stop spending money on tattoos." (I have three).

These are ladies who have "careers". They dress spotlessly, in pearls and heels, host wine parties, perfect homes, husbands, kids. They are the typical "perfect" lady. I am the opposite- sometimes I wear a comfy pair of jeans and a ratty tshirt around the house. Sometimes I buy baked goods for a party instead of doing it myself. I am frugal, have done several part time jobs to get by, only buy on sale, and they say I'm "on glue, drugs!" or I'm "a hippy dippy who needs to shake her head".

I am pretty happy with how I live my life- my kids are super happy, I am generally happy... our furniture is a bit worn, I don't always dress in the height of fashion, and I am far from perfect (I don't even try to be!).

I don't quite know how to deal with them. I don't even TRY to impress them or call to chat... though they constantly tell me how close they are, how much they value each other, etc. I know their brother and I have had major issues, but I feel like they just think I'm trash. I have never cared about what people thought of me, but for some reason they are really really getting to me. I know they talk about me, and how "weird" I am, and it just... is really upsetting me. My husband has talked to them about it, and they just say "So? What, are we supposed to pretend we LIKE her?!"... help! How can I deal with this, or get over it?