So I went through my LTR's phone and found something. Nothing recent but concerning.

I plated her for a few months before accepting her offer to be monogamous. I told her to give me a few days to cut the people off. She also told me that she was occasionally seeing this guy who she needs to politely tell off (because of common circles)

After gaining commitment for me she met this guy 2 times - in the next 14 days and apparently did not tell him off or anything. After that the texts became sparse and a month later when he texted her asking how she is doing she says (paraphrasing) - You are a great guy but I don't think anything can work between us and that she can't be more than friends.

After this text occasionally and then stop texting altogether.

This happened about a year ago at the start of the relationship. I found nothing else on the phone on any apps. The relationship actually got better with time and she has in all senses I can see been a good LTR (ample sex, cooking, doing things for me, buying gifts etc.)

I am torn what to do because this looks like almost cheating.