Dealing with Boyfriends teenage daughter..?

My boyfriend of 9 months has a 13 year old daughter who is the moodiest, hateful and rude yound lady I have known. The relationship between my boyfriend and I is sincere and solid, and we have made long term plans to one day co-habitate, and or marry. We were friends for several years before dating and have grown quite fond of one another. We love each other dearly and have a honest and close relationship. The problem lies with his daughter... I can hardly tolerate her behavior at times while she behaves rude and demanding of her father. Asks for money to go to movies or other events and then tells him to "go away now". She shows no appreciation of her father being generous to her demands. I have a tough time swallowing her disrespect and rudeness toward her father. She is very moody to the point of perhaps being bipolar and his family recogonizes this. I prefer to keep my distance while he has visitation with her, as Iam on edge and biting my tongue to tolerate her behavior. I have now began to ponder whether the is a relationship that I want to pursue long term...due to the fact that she is only 13 and it will be 5 years till she is on her own and the opportunity would arise that we could pursue spending our future together. I would never survive living with him while she would still be having visitation on a regular basis. The mother has a hatred for the father and feel that this attitude is being instilled in the daughter, The mother doesn't hesitate to tell the daughter that she hates her father and the daughter then tells dad of the comments that mom has shared with her. It seems she has accquired her own internal hatred from the influence of her mother- who is the full time parent. I love this man and aside from the stress of his daughter have no reservations about making him my partner in life. Is it worth a 5 years wait to endure this torture? Or do I move on...?