I'm going to break up with a girl the day before valentine's day
Why break up with her before Valentine's day?
I have been though a lot because of her. I don't want to deal with it during a holiday.
It's not very nice to break up with someone right before a romantic holiday. You should at least wait until after it has passed.
It's not that big of a deal. She would probably want to break up.
Well if she wants to end the relationship, then it is okay. It is better to end a relationship than to continue to make each other unhappy.