Long story short, my LTR girlfriend who has been living with me for 2 years was showing me a pic on instagram and I accidentally scrolled left right into her DM page. I saw a very recent conversation there that was with her ex bf. I wasnt sure if she saw me see it, so i gave her back her phone and looked up the name on my instagram and confirmed it was her ex. She immediately deleted it sneakily hoping i didnt actually see it. However I did, and I asked her who that person was. She says "who are you talking about?". She shows me her DM's and now its only the DM with me. She deleted it and lied to me about it. Then I gave her the exact name of the person, and she said it was a friend. I said thats your friend? Then she said it was her ex boyfriend. Then shit hit the fan and crying ensued and all this bullshit about how she didnt want me to to flip out over something so stupid.

She told me that they were just talking about innocent shit and that she was helping him with some problems (horse shit from a mile away, then why delete it or hide it behind my back?). I later convinced her that I had a program to trace back the deleted message so she started giving me more details about the message. She then told me he had sent her nudes/dick pics but she swears she never sent anything back picture wise, but she did continue to entertain the conversation even with that shit sent to her, ultra red flag. She continued the conversation after dick pics were sent, and Ill never know the actual content. The entire conversation was behind my back, and I would have never known about it unless I accidentally stumbled upon it from her showing me a picture.

This was a serious relationship and she blatantly disrespected me and lost my trust completely. I actually believe her that she didnt send any pics back, but that doesnt really matter at this point. It is the fact that it was all done behind my back and without respect to our committed, serious relationship. And also the fact that the conversation continued after pics were sent to her. I know what I have to do, I just want to hear some opinions on the matter just to validate that what she did was unacceptable.

With all that said, she is otherwise a great girl who supports me financially and has never lied to me before. She says she will do anything to earn my trust back and she is absolutely petrified of me leaving, and she hasnt left the bed in like 36 hours. I think that this sort of thing is unforgivable. AM i wrong?