Relationship problem, need advice please?

My bfs friend thats a girl wants to hangout with me and him. Im convinced she likes him because she always asks him for advice and texts him non stop and is obsessed with hanging out with him, not once has she came to ME and asked ME to hangout with us..I said ok, i want to get to know this girl more if shes gonna be so close to my bf, so we planned for her and my bf to come over my house next week, now i found out from my bf that the two of them are hanging out tomorrow without me? I want to ask him why he needs tO hangout with her alone when we'll all hangout next week, i just dont know how to state it and i dont want to start a fight and seem jealous, i just am concerned about this and very suspicious, i trust him but i just wanna ask him why they need to hangout without me again when we're all gonna hangout next week. Btw i live in a different town (15 min away) from them two so im sort of at a disadvantage of seeing him as much as...please give me any opinions or advice, sorry for spelling errors im kind of rushing this !