She freaked out and ran out of the bathroom.
Wow, was it because of a bathroom prank?
Yes, she got angry and decided to leave me.
It's rude to deliberately scare someone, especially in the bathroom when they expect to be alone and in private.  This might have been a harmless prank, but your girlfriend has a right to be angry with you for terrifying her like that.
I'm not mad or upset, I knew she would freak out. I am in fact happy
People would like to use the bathroom in peace and playing a prank is so mean. Like do you not care for your partner? IS she ever coming back?