MIL issues

My husband and I have been married three years. During this time, my mother-in-law and I have gotten along fine but we aren't close--at all. She doesn't have my phone number, and I don't have hers. My hubby is the only child out of three who is married and his mom has been divorced and dating the same guy for years. 
Little background: His whole family is high school educated (which is perfectly fine), don't have much money, and are Very open in terms of talking about sex and bodily functions. Oh, and his moms boyfriend is an alcoholic. My parents, while not rich, are upper middle class, conservative and my whole family has either a Bachelors or Masters degree. They are also highly religious.
Things have been fine until his mom and her boyfriend moved to our town. She works part time at Walmart, stocking inventory. Her boyfriend walked off his last job because it was "too hard" so she is their sole source of income. They live with his grandparents because they can't afford a place of their own, and she is already talking about quitting HER job and collecting unemployment until she finds something else. I have a hard time being sensitive towards this because it is PART TIME for one, and she stocks inventory...I have worked in a county jail for over three years-12 hour shifts, rotating days and nights every two months and dealing with inmates flooding cells, throwing feces, fighting one another, attempting to attack officers, etc on s daily basis. Yet I don't quit because it's "stressful." There are bills to pay.
She got upset that my parents joined all of us for dinner on Christmas <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">EVe</a> and spent the night with us--they live in another town over two hours away. She is also upset that we go visit them most weekends I'm off, even though we go visit her at his grandparents and have told her she is welcome anytime. She told my husband she feels like he is treating my family like they are "more special" than her. I suspect jealousy, but does anyone have any idea how to move past this?? It's like she is guilt tripping my husband for spending time with my family. 😡