Mother asking for a small monthly contribution - am I unreasonable?

Assalam alaikum, I shared something here before so some of you might remember me. My dad is in really bad debt and the rest of the family doesn't fully know how deep it is. While this was happening my mum's physical and mental health collapsed because of things my father did (I won't go into details). She was in hospital for months and was diagnosed with a functional neurological disorder - basically her depression has physical effects. At one point my dad was so desperate he asked my mum to put her hard-earned savings into an account supposedly to build a new home for the family. I told her not to, because I didn’t trust him emotionally, but she did it anyway. He then spent the money on who knows what - maybe to pay debts or send overseas, nobody really knows - and now when asked he just says, “I don't remember.” My mum has little to no money left in her account; she couldn't even use her card for $15 at the shops back then. Lately my dad does more basic housework than he used to when mum was healthy (and she literally used to do everything), but it feels minimal. He seems to rely on a credit card for bills, groceries, petrol, and I’ve even seen loan applications in his emails. Now mum has asked me and my sister (we're both under 25) to give her 50 AUD each month. She asked about how much we get from the government, guessed we each make about 1k a month, and decided 50 was a small enough amount. I felt annoyed that she asked us instead of asking her husband. I know she's vulnerable and I feel bad for hesitating. My sister probably won't want to contribute - she has a more “I don't care” attitude and doesn’t carry the same guilt I do. I used to earn 500 AUD a month until recently, and the extra income finally lets me save. When I asked mum why she wouldn't ask dad, she said he doesn't have money - which might be true, but isn't that a sign he should be stepping up and working harder? He took mum's years of effort for granted and, honestly, credited himself for things she managed. This whole request, astaghfirullah, frustrates me. No one in this house has really acknowledged what I did when her health first collapsed, and we as children have been emotionally neglected. Asking my daughters for allowance instead of the husband feels unfair. I need emergency savings for my car, I want to travel, I sometimes pay to take my three sisters out so we have some decent memories, and I send gifts to generous friends who live out of state. My sister is saving for a car too. I'm scared and overwhelmed by these money problems and the marriage issues between my parents - sometimes it all feels too much. Is this a reasonable thing for my mother to ask of me, or am I being a spoiled brat? Any advice would be really appreciated. JazakAllahu khairan.