I'm not going to take my girlfriend to her hair appointment
What is your issue with taking her to her hair appointment?
She spends way too much money on herself.
That is your girlfriend's money, not yours. She has the right to buy whatever she wants. She also needs your help, so take her.
She should know how to take care of herself.
You should do your best to do something nice for your partner when they need it. If you continue to refuse to do anything nice for your partner than they are simply going to leave and find someone who will.