What should I do about my bf’s relationship with this girl?

So my boyfriend whom I intend on marrying someday (and he feels the same) has a friend. He’s her best friend but not vice versa. They slept together a few times a few years ago. She was in love with him. He wasn’t in love with her. I’ve hung out with her with him and a group of friends a couple times. I knew something was up but never brought it up til recently. I discussed my feelings in a nice manor.

He said they don’t text much and she asks him to do stuff but turns her down. Well he gave me permission to look through their texts and I was like “nah, I trust you. I just don’t like how she acts around you.” He got that.

Well I was feeling uncomfortable and did read through some of the recent texts. It looks like he’s deleted some texts... they were responses to her “hey wanna grab a drink?” Or “hey busy Sunday?”

But even though I don’t think he’ll go. I’m still uncomfortable that he deleted texts??

I KNOW he would never cheat. But it doesn’t make me any less uncomfortable knowing they had a past.

I really don’t know what to do or how to feel.

I don’t feel right asking him not to hang with her. Or talk even. I’ve slept with a friend before too. But I don’t talk to them or hangout with them out of respect.

What should I do?