It is definitely not a requirement. It's your money and your decision what you do with it.
I'm of the opinion that you don't owe your parents anything for bringing you up. Your mum brought you into the world so it was her responsibility to bring you up. And, like any adult, it is also her responsibility to fund her own lifestyle.
Perhaps, I would lend my parents money in an emergency but that isn't what's going on here. Your Mum is making it clear she doesn't even intend to try and provide for herself. 'when I'm broke'. How about working and not being broke? That is laziness and I wouldn't be having any of it.
I would make it clear to her now that she is not getting any money off you.
My parents haven't asked and I'm sure they wouldn't but I wouldn't give them money even if I was earning 6 figures. Why should I? The haven't given me anything. In fact, even if I won millions on the lottery, I wouldn't give them anything.