I 26m caught my girlfriend of 5 years 25f in a lie.

To get straight to the point my girlfriend has been caught in a lie but she doesn’t know it yet and I don’t know what to do. I will start by saying our relationship the last 5 years has been amazing even up to today. My girlfriend holds a head manager position at her job and is in consistent contact with other location managers. Well there is this one guy let’s call him Mitch and out of all of the managers (majority female) she likes him the most. Well maybe 6 months ago I saw her phone open when she left the room and snooped because I was intrigued on what they talk about because all I’ve ever heard is how cool he is. I did not find anything bad but was surprised how often they talk. She works 8-9 days and was texting him from like 9am until 10pm and night. I got really jealous but left it alone because all they had talked about was work, memes, and played I message games. I had communicated that she talks to him more than me and was kinda strange even more so that he has a girlfriend but they talk ALOT!

I have tried poking around about him to her about a week ago and she says she barely talks to him. Unfortunately I snooped again the day after on her phone yet had no texts with him. Well with the newest I phone update you can see deleted text messages if they haven’t been deleted from the deleted folder and we’re over a 100 texts deleted hours before she had came over that day and is hiding it from me.

I am kind of lost on how to proceed and what actions I need to or not need to take. We have a great relationship but why is she lying?

TL;DR : 26m caught my girlfriend of 5 years 25f in a lie and hiding texts messages from a co worker.