=\
Sounds like one of my friends at school.. There must be a reason why you two got together in the fisrt place. I'm sure she may have a reason, some girls can act differently and stuff.. and have you ever considered that she might be on her period cause some girls can get a little bossy on their period; unfortunatly
Best bet is to like be careful what you say and make her happy if you can but if it continues where you two keep argueing thn I suppose then there's no point being with her, cause to be honest that's not really a good relationship if you keep argueing.
I hope you have good luck with her and things get sorted out.