My girl friend break up with me?

Last weak during canteen day at school,i went to watch movie with my friends(boy) and also my ex followed my friend.but i didn't even talk to her.i was siting with my male friend all along.but before i went to the movie i was finding for my gf all over the school so i can go watch movie with her.but she wasn't there so i had to follow my friend but i didn't even aspect my ex to follow my friends.honestly i didn't even talk to her.now my gf got to know i went to watch movie with my ex.and she wants to break up..she says i lie to her by not telling her i went to watch movie with her.but its is not even a big thing..i didn't even talk to my ex .i was with my friend all along..she says now she wants to break up..don't she understand how i feel?what should i do?please help me.i trusted my gf that is why i didnt tell her?but now... :(My girl friend break up with me?
tell her the truth. let her know that you never said a word to your ex and that you went with your friends. tell her that your sad cuz couples are supposed to trust eachother.My girl friend break up with me?
Well, you can never expect to you girlfriend to broke you up just because of that incident happen,most of the girls are jealous so maybe she's jealous of your ex-girlfriend. Just talk to her and invite her foe dinner so that you can explain what happen on that day.