What does all of this communication between them, mean exactly?

My boyfriend which is in his mid 30s and I which have been together for almost 3 years, has been communicating with a girl (27) that he calls a friend that he knows from some time ago and supposedly knows her family as well, as far as I know, he’s been talking on and off to her the whole time of him and I being together, she lives in a different state than him and I do, so she is far away.but she does live very close to the state that my bf is originally from.

When him and I started dating I remember he talked about this girl a few times and he couldn’t understand certain things surrounding her and her marital issues/Problems and he tried helping her and still does, I did not care at that time very much to be honest, in the back of my head I was like yeah ok whatever, but several months, I do recall it creating certain doubts in me, and questioning myself of who is this guy really and what’s his past!

So recently we were together and he was telling me that she had contacted him, because she is going trough some ’‘rough’’ issues and he needed to help her because it was serious, he told me she comes and goes looking for his advice or when she has problems, He seems very connected to her and My thoughts are: 1-This girl is either using him as an emotional dishrag and he likes it for some reason 2-the most obvious she is an ex-lover and there is an ulterior motive behind all of this chit chat, or 3— there is something more to this that he is not telling me.