SUBREDDIT: r/relationships
TITLE: Me [20M] with my girlfriend [20F] has been dating for a year thinks I am too friendly with my girl friends
POST: I think I messed thing up forever. For awhile now my girlfriend has been very apprehensive about me chatting with my girl friends. She thinks that I am too friendly with them and flirty. I do agree with what she is saying but today she read through my messages on Facebook and found a conversation I had with a female friend in which we agreed to hangout more in the summer, in a friendly way, which she thinks that I have reverted back to me being a flirt. I thought that I was pretty blatantly joking in the messages about being best friends with her or coming over to her house and eating dinner etc, but my girlfriend thought that it meant I was being way too friendly with her.

 I think that I fucked things up forever. She now doesn't want to talk to me and is thinking about ending things with me. Anyone have any advice regarding this situation?

She has been my life this year and I love her so much. I know that she is the one for me. I know this for sure. I've thought about spending the rest of my life with her and I would do anything to keep her happy.
TL;DR: 
Girlfriend thinks I am an asshole for being overly friendly with a mutual friend, thinking about breaking up with me over it.