Sounds really hard. I WILL say that your partner sounds like an honorable man. That's the kind of guy you WANT To be with. The kind who feels loyal and responsible to the people in his life. So, cherish that. And try to support him. I know this is really hard and I would hate it as well.
What can you do to help encourage her? Maybe you and your husband could right out a budget. Think about how much you would like her to contribute and don't leave it open ended. let her see the bills. Make it all very real. Let her know how much your partner brings in. And then give her an amount that she needs to pay. And have a date by which she should start paying. I would write it out and have that amount for three months with the option of requesting more after that three months. then she knows what is expected in black and white. Have a family meeting. Go over this. If she can not find work, then her 'rent' will be her babysitting. Explain it to her officially and then act on it. If she isn't babysitting and working, then you present her with a move out date and you can tell her that you'll help her look into welfare to support herself since she refuses to work. But that you have two kids, one on the way and money is too tight to also pay for her at this point. You love her (or your partner does) and want the best for her but have to be realistic.
Then make a division of labor chart. Have jobs for yourself, your partner AND her spelled out. Hang it up in the kitchen.
It's hard. No, not al mother in laws are terrible as stated above. That's very untrue. And having someone completely out of your life hurts---- even when we don't know it. So, hopefully this can be worked out. I certainly can understand how you feel--- this would really bother me too. Hopefully it can be worked out hon. good luck
I'm sorry that you are going thru that . Mother in law will always be a pain in the ***. Thank god I don't have that problem because mine never wanted to meet me. My husband and I have been married for 8 years and we never seen each other, thank GOD. Good luck Tricia