Am I in the wrong?

Recently my mum has given me a lecture as to why I should be giving her money to help out.  She wanted at least $100, I was thinking monthly should be okay, but she insisted its nothing and she needs it weekly! She doesn't work due to an illness, but my dad does and she gets gov payments. We're  managing to get by but the reason why I'm so annoyed is because I have so much of my own stuff to pay for! I pay $200 a month on my braces, about $100 for my phone, $45 a week on petrol, $180 on car insurance, plus I have to buy myself anything I need such as clothes, toiletries, and recreational stuff. A few days ago someone smashed into the back of my car and doesn't want to put a claim through so I have to pay for that now. I also bought my own car and just finished paying off my loan so I have only just started trying to save. I'm only working a casual job so my income isn't steady and I'm getting really stressed out because if I tell my mum I can't afford to give the money this week she starts an argument with me and makes it out like I'm the most selfish person in the world and acts really bitchy and it makes me feel like shit. I love her and all cause she's my mum, but I know she has a bit of a gambling problem and I've got a feeling majority of the money I give her does strait into machines as she often goes out and comes back with no shopping bags etc when she says she's going to the shops. 

There's no easy way out of this cause I tried explaining why I can't afford It at the monent and she just kept calling me a liar. 

Any advice on what I should say or do? 

Sorry if that makes no sence but I'm crazy stressed really needed to vent 😔