I think I'm not going to lend money to my mother.
Why do you refuse to lend your mother money?
I can't afford to give her money.
Even though your mother needs money you do not have to lend it. It is perfectly fine to keep family and money separate. If you lend money to family constantly you could end up broke and in debt.
Fine I will have to spare some cash from my tight budget. For her only.
As long as it doesn't hurt you financially then I think that is okay. I'm sure your mother will appreciate it.