<human>: So her brother told me that she dated this guy. I had a suspicion before, and when I saw him race through her Instagram liking everything, I said "So I see your ex, John, is back," as she told me she dated someone with that name. She said (with sass) "I dated a Jon, not a John!" (actual name different, but similar story).

She deletes her texts everyday. However, I ordered pizza a couple weeks ago on her phone, and saw 3 calls between them in the call history, when I was away on holidays. 2 were missed calls from him, and 1 was outgoing from her to him, 45 seconds long.

I don't know what to say, I've already brought it up and she denied they dated. The brother could be wrong, although unlikely. 

They snapchat when I'm not around. He followed on Instagram, she didn't follow back, likely because I may see it on my feed if she followed someone. They've been friends on Facebook since 2007 or something. Likely high school friends, but none of her current friends are mutual friends, so I don't know anyone else who knows him.

I have seen a couple texts on her phone back when they just started talking 3 months ago, when she forgot to delete everything, he's basically guilting her into meeting up for coffee because he needs an ear.

Can you condense the text into a few key points?
<bot>: GF deletes texts, misses phone calls from a guy who may be her ex, but I can't be positive. How should I approach her?