<human>: Can you succinctly summarize the text in 1-3 sentences?

I want to know if I really am overreacting or if I am okay in being upset and what sort of advice on handling the situation better.

I have been dating my girlfriend for 1 year now, we are both 22. The other day we go to a bar with friends. We all get drunk, good times had. It's around 1am and I notice my girlfriend was texting a mutual friend who is known as a bit of a womanizer. The only texts I see are her saying "I miss you" and "let's go on a coffee date soon, Kay?". So I didn't want to make a scene so I blew it off and brought it up today because it had been bothering me. She admits it's weird but then when I begin to explain that it seemed inappropriate she starts getting pissed, saying that she shouldn't feel bad and that they are just friends (which I believe) but saying it was not inappropriate and that she has nothing to feel bad for or apologize for. My point was if I received a text from a drunk girl friend of mine saying the same thing, I would tell my friend it was inappropriate to say because I have a girlfriend and she was drunk. She then told me to leave. How should I handle the situation from this point on?
<bot>: Girlfriend sent "I miss you" and "Lets go on a coffee date soon" to a guy friend while we were drunk.