Appreciate any honest advice.

Backstory: known this girl for a year, plate for 6 mos and LTR for 6 mos. She has lots of green flags: good with money, good job, low body count, hb8, good sex, always cooks and cleans, supportive

Looked at gfs phone today and saw she had a Snapchat from her best friends boyfriend. Looked closer and saw she had a 62 day snap streak with this guy. (They had about 20 messages in the last couple days alone but it was all platonic, nothing flirty). I thought that was weird and called her out about it, but she tried to play it off and said they were just friends. She claimed that she had been helping him pick out a ring for a proposal and just kept the streak going.. I’ve met this guy before and always thought he was sketchy and know he has cheated on his gf before.

Anyways I go through her phone and don’t find her talking to any other guys. And don’t find anything suspicious at all. She right of way said how sorry she was and deleted her Snapchat and told me I could look through her phone whenever I wanted.

The whole situation was way too suspicious for me. I don’t think she would cheat on me but snap chatting a guy for two months straight even if it’s platonic is still not okay with me. I packed my shit and walked out of her place. I’ve been cheated on in a past relationship so I don’t take this stuff lightly. Did I do the right thing or did I overreact??

TLDR: saw my gf had a 60 day Snapchat streak with her best friends boyfriend. Went through messages and couldn’t find anything else suspicious. Packed my shit and left anyways.