My niece goes to college in my city. She used to rent an apartment with one of her friends but then her friend dropped out of college and moved back to their city and she can no longer afford that apartment. She hasn't been able to find another roommate and asked if she can move in with me.

I have an extra bedroom so I didn't see why I shouldn't let her. She moved in with me a few weeks ago.

Now my gf is mad at me and wants me to kick her out because she wants "more privacy".

I was honest and told her that I've known her for a year only but I've known my niece for 19 years so if she tries to make me choose, it won't be her, it will be my niece.

She thinks I'm an asshole.