Girlfriend hiding something? I need an advice.

Before you start reading, yes I might be overthinking. Introduction: Me \[22M\] and my gf \[20F\] have been together for 4 years, there have been ups and downs ( there was a lot of jealousy ) for an example I was following many girls ( from my highschool that I personally knew ), I had nothing intimate with them and would hang out as a group with male and female friends. In response she would hang out with her girl bsf on purpose when there were some random guys around. All of this was happening prior 1 year ago, now it's "normal" and we're happy with each other. In the end, we set up a strict ( bit toxic ) rule: I can't have girl friends She can't have male friends **Main part**: Her girl bsf works at a caffee as a bartender, and my girlfriend always sits at the hightable closest to her. Since it's a small town, locals always sit there and chat ( usually older people ), her friend got used to it, so it's social interactions ( she has a bf and there's nothing going on ). The thing is when my gf goes there, there's always someone's already sitting at the hightable and she can't really ignore the guy that's already there, that's normal and I don't mind at all. They sometimes offer her a drink, she accepts as a "free drink" and that's it. This time, that guy \[28M\] also offered her a drink, as usual, but this time he asked for her Instagram and they followed each other, when I asked why ( especially after we talked about not following other guys/girls ) she said that the guy told her "we are all locals here etc. ), ( that guy also has been following her bartender friend from before ). That kinda sparked something in me, I'm jealous but still doesn't sound odd at all. When I told her how I feel, she offered that she can unfollow him. That guy will still always be there at the bar and I can't really do anything about it. \- **The only left assumption I have:** I was insecure and had to look at her dms, he wasn't there, but when I clicked the "search dms" bar at the top of dm's, he was at the top shown as "Recent", under him was her girl bsf and then me ( she doesn't have a lot of followers, usually talks to like 4 people including me ). Why was he at the top? That instantly made me have doubts again after I cooled off and thought she deleted the dm with him. When I checked 2 hours late, he didn't appear there anymore. I searched up on Google and it says Instagram algorithm sometimes shows new followers at the top of that dm-search-bar, but when I tried to do the same with my alt account ( I followed myself from there to my main, but in my search bar I wasn't there, only the recent chats and people I had chatted at least once ) Any advice would be helpful, we never had big fights and we love each other, but this all of a sudden made my heart drop. tl;dr I'm sceptical if my girlfriend is interested in another guy, after 4 year relationship, they both followed each other on Instagram after one talk at a caffee where her friend works at, is there a way I could tell if she's deleting chats with him?