Listen to Eric...Breathe...Slow down the pounding in your chest and head.
So why do you think she is talking with the OM again? At first it read like you caught her texting him (actually visibly seeing or snooping on her phone) and then it seemed like you were accusing her because she wouldn't share the phone records.
Each is different...in it's own way.
As Mr. Bond said...If she is merrily texting away after your conversation, Then a boundary needs to be put in place. Are you ready for that? Boundaries are only as strong as the person putting them up.
If you are coming to the conclusion that texting is going on because she won't share the phone records.....Well that is different.