I don't want to visit my crazy aunt for Thanksgiving.
Why don't you want to visit your crazy aunt?
Because she has mental issues. I don't want to spend time with her.
Even if your aunt has mental issues, that shouldn't be a reason to avoid her during the holidays as that is the time for families to get together. You should still make the effort to visit your aunt as she would be very emotionally hurt if no one visited her during Thanksgiving.
She won't be hurt. I'll say that I have a big test and need to study.
It is good that you have an excuse so that she doesn't feel hurt but you should still try to be there. Family is important and so is spending time with them.