<human>: Can you provide a brief overview of the text?

My girlfriend(F26) and I(M33) have been in a long distance relationship for about 4 months. Because of the distance, we've been seeing each other only about once a month but text and call throughout the day everyday. We met roughly 5 months ago.

We had plans to meet the weekend after Valentine's but she cancelled to attend a friends going away party. While at this party she ended up making out with someone who she met while there. Alcohol was involved but she said she was not that drunk. She told me the following weekend shortly after meeting up. We have an enormous amount in common and have never not gotten along.

Our relationship kicked off and moved pretty fast but we were both okay with it. Both of us expressed our love for one another and planned on moving in together in early April.

She seemed sincere when telling me how sorry she was and is aware that my ex-wife and a previous long term gf cheated on me. When I asked her why she did it she claims that she simply does not know. I am very emotionally confused. I love her and half of me wants to try and work through this while the other half wants to run. I could really use some advice and will gladly answer any and all questions.  (On a mobile so it may not be as in depth as it should be)
<bot>: girlfriend of 4 months kissed another guy while at a party. I would appreciate advice on staying with her or breaking up.