I'm not going to donate to a community member that got leukemia
That's unfortunate. Why don't you want to donate?
She is completely uninteresting. She wears the same clothes every single day, she's boring and she doesn't care about other people's feelings.
She doesn't sound like a great person. It's fine to decide for yourself what causes you want to help with. You don't have to donate to someone just because everyone else does.
I'm the best person to decide who I should donate to.
It definitely is your choice to stand your ground with your morals. It may be unfortunate she has cancer, but you aren't obligated to donate just because of that. I'm sure people will understand, especially if she mistreats others.