Im a 30 yr old male engaged to a 30 year old female(Rose) in another part of the state. We are now in this long distance relationship, and I understood within a few month we would move in together and get married, in that order.

My fiancé has a younger sister ( Mary) (she is a single mom) and my girl has always been there to take care of them both. They have lived together always. Rose has been like a mother to her sister and niece.

Now that Im in the picture, and Mary moved out of the house (to be with her dad) I make plans to drive 300 miles go see my fiancé every two weeks until I move over there in Sept. Her sister decides to go to Rose's house also, (she drives 200 miles) making me feel like a 3rd wheel.

Rose can't stand the fact that I do not want to spend time with her sister. I just want quality time with Rose, just the two of us. I have offered alternative weeks to go see Rose. But Mary will just show up knowing I will be there.

Rose is torn because she loves her sister and niece, no matter how far in advance I make plans to go see Rose, her sister Mary will drive two hours to Rose's house and stay the whole weekend with us.

Mary is is 26. a grown up women with a child. She does not feel she is intruding, and Rose will always take her side when I tell her about my discomfort.
And does not want me to say anything to Mary.

I love my finance, and I continue to go to see her even though I am not happy about the situation. I don't want to break off with Rose, she is everything to me. Its her sister that bothers me.. I don't know what to do.. I want to marry Rose.

Any advise on how to handle this?
Thanks,
J P