Recently on a vacation we were in the casino after getting a nice dinner. We were all dressed up, and I saw my gf send a picture of herself looking nice to another man I've never heard of. I asked her who she was texting and she said it was a group chat. I know I saw another man's name but I didn't push any further then.
For some background, we have been going out for 2 years, and I took her on this trip as part of a birthday present. A couple days after we got back I facetimed her (we don't live together) and I confronted her about sending a photo to another guy. I said the guys name and she said she doesn't know who I was talking about. I kept pushing and she said that the group chat was named after people. Obviously this sounded like bs so I kept pushing and eventually said the guys full name which she then said she did text him. She is in the army reserves so they refer to each other by their last name which is why she claims she didn't know who I was talking about at first.
Obviously I was upset and I asked if anything was going on, why she did that, why she lied about it twice. She said its because she knows how guys view that thing and since she is in the army she knows a lot of guys so she views it as normal to chat with friends or send pictures. I asked to see the chat message and she said she felt uncomfortable doing that due to her last relationship being controlling.
She does things that seem like she genuinely cares about me, going out of her way to make food for me, being nice to my mom and bringing her gifts etc. I don't want to end things with her but I find myself distrusting everything she says lately. Plus she has to go for training once and month and I don't know if this guy will be there or not.
I know how this looks, and I can't get it out of my head as to why she would lie about and double down. I'm wondering if I should just slowly detach from this wait to see if more reveal itself, or confront her and try to get some clarity or closure, at least get her to admit what is going on so I'm not going crazy.