I don't know for sure, but if he hasn't been mentioning her for two years if he had something to hide why mention her at,all. If there had been constant drama with this woman the whole time you were together, and your bf was constantly inserting himself into the situations, then I could maybe see why you would be worried.
Tbh though he avoided getting involved before by asking you to pass the details onto her.
If something was going on between them do you think it likely he would encourage you to talk to her at all, for any reason?
If this was a guy friend would this even be a question?

Guys have a tendency to offer good solid practical advice which might be what she needs, we just don't know.
If one of my friends was separating from her his partner, then I hope I'd be able to offer some help.

Maybe as Mickey says it would be best to just talk to him about your suspicions.
But it's only worth asking him if you are going to believe the answer otherwisewhats the point.

Hope it all works out. Take care.