I'm going to break up with someone because they were mean while on their period
Is she mean while not on her period?
No.
If she isn't normally mean then I think you should try to be more understanding and forgive her for the way she acted. It's understandable that sometimes people don't act their best.
Yeah, but it is getting old. I need a break so I am going to be single again soon.
I understand, and it's your choice if you want to break up with her. I just think you shouldn't judge her so harshly for something that is out of character.