Hey and welcome,
I am in an newly established vee as well. Same structure, nearly the same initial position as yours. My husband seems to be as positive about my boyfriend as you are. I had a hard time coming to terms with the relationships and my feelings but you don't seem to have those issues if I interpret the tone of your post correctly.
I think it is acceptable to ask for the motives of the boyfriend. But maybe this should be done by her first. My two men are in it with the intention for long term commitment and they know each other some time. So this kind of talk is daily routine. But it could come off as pressing and uncalled for if you do not know each other.
I absolutely love it when my men do things together. Or make up their minds over matters that broach the topic of living together/being in contact with each other/spending freetime together. I love to see them developing a relationship of their own. If you click well with the new friend, than this could be a great help of making the relationship run smoothly.
My husband wanted to meddle too much in the beginning in fields that were just off limits for him, because he wanted to be involved. You need to communicate how much is ok and how much is just too much. But I think they will be able to tell you what is ok and what not. Ask her if she has already talked about his commitment and thoughts of the possible future developments. If she thinks that it would be ok for you to ask him about that.
Good luck and all the best