Am I selfish for not wanting to help mother n law

So my husbands 73 year old mom (gma) is 3 months behind on rent and behind on other bills. She lives with her 50 year old son thats a druggie and drunk on the street. She constantly gives him money and gives his kids money when they ask. So she's always broke. He sells her foodstamps and pawns all of her shit. So she always asks us for money and food. I was feeding her every night for awhile and she would complain that our food is shit because she's so use to fastfood. She has stolen items and money from us and im so sick of them. They constantly ask us for stuff and rides. I'm so over it. So today she asked us for $600. We don't have it. And if we did it wouldn't go to her. So she asked my husband if he could co sign on a loan or refinance our truck to give her some money. My husband told me he wasn't going to do it. But took her to the bank later and tried for her behind my back. Thankfully they got denied. I'm so mad. She would never pay us back and I can't believe he would even think to do that. I know it's his mom but she doesn't really talk to us unless she needs something and doesn't bother being in our sons life. Am I in the wrong?? **EDIT** we have tried to get her out of the situation but refuses to be with out her drunk son. She wont kick him out or leave him. And gets mad at ppl that try to get him out of her house. I love my husband he is a really good man. Even tho his mom treats him like shit hes still does everything for her. But her asking everyday is starting to make us argue alot. She just asked again today and wont leave us alone about it. My husband says hes not going to do it anymore but i have yet to hear him tell her no straight up. I dont want to leave him but we have been doing everything for her ungrateful ass everyday for 16 years and im over it.