I'm simply going to repeat what others have already said...
1) She's already cheating.
2) Yes, if they had the opportunity, chances are very high they had 'some kind' of sex. At a very minimum, based on what you say the OM said, it was absolutely tracking in that direction.
And as someone already said, it's up to you how you define 'sex' and whether it matters at this point to you.
I'm kind of in the same boat. WW was in a full on EA with sexting (x-rated pics, dirty texts... all that) with some random OM she met online, but the OM was in an entirely different state, so physically impossible for that to have become a PA, but it definitely would have.
When I caught it, they were already floating dates and locations to meet in-person based on a possible trip my WW was planning to take in his direction (for a completely unrelated, personal event). Even if she did make that trip, it would have been a few hours for him to drive to meet (or a short flight). My WW tried to claim that they just wanted to meet to 'get to know each other a bit more personally'. I totally called BS and said I'm sorry, no guy who has been exchanging those kinds of pics and messages to someone online, drives HOURS to just 'to get to know them'. Even if my WW wouldn't admit her true intentions, I told her HE certainly was planning on having sex. When I put it that bluntly, she just looked blankly at me for what seemed a very long time. I asked her, "am I correct?" And she basically agreed, which was then a tacit admission to me of her real intentions.
On top of this EA, during this same period of her having the EA, she also met a guy when she was out on her own one night and wound-up in his car. At first it was just some kissing, then it was, "ok we made out, but nothing more, no touching beyond the kissing, nothing" ... riiiight.
To be fair, I do struggle with did they or didn't they, because there's no proof they did. They will ONLY ever admit what they did when there is evidence, but I've been on this forum long enough now... I'm not naive. I believe they did.
Anyway, my point is, even if I had definitive proof they didn't, it doesn't matter anymore. She's a cheater.
So back to you. You probably need to accept if they had the opportunity, they had some king of physical, sexual contact, but again, how much does that matter to you given what she has done.