should i just ignore this?

[Guest]

i am with a guy who is rather handsome, but also i am a nice looking girl too. he is one of many brothers, and his brother is similar looking to him, ie handsome. i love my boyfriend and his feeling is mutual. we have been going for a while. we have had a nice relationship with his family (his brother) until about a year ago, when his brother starting going out with a girl with strange behaviour. she is from a different country. i noticed from beggining she did not like me just from the way she was very unfriendly to me. she behaved in a very show off manner whenever i am around and would say quite nasty things to my boyfriend about me for no reason. my boyfriend then proposed to me and she did not even congratulate us. whenever we see his brother and the girl, she is very unfriendly to me but friendly to my boyfriend. if i am around she will put on a show, wear something very provocative (and usually inappropriate) so that all eyes are on her and she would boast in front of their parents/friends how great is her career, her life, her relationship, whilst totally ignoring me and my boyfriend. it is all very obvious. very often she would wear something inappropriate like hot pants for family dinner and kind of everyone is uncomfortable apart from her and her man. to add to that, i am not so conservative/ prudish and i am not unattractive but rather attractive girl. however i do not have a need to provoke people or family in this way. in addition i have an interesting life and career but i do not boast about myself in that way however i do not like to be ignored and shunned by people in consistent manner. recently she started sending pics of her and of his brother on vacations, to my boyfriend's email only - pics of her posing in bikinis , kind of provocative - very self promoting.. my boyfriend then shows me these pics and we do not quite understand what her point is. we are getting married shortly and this behaviour is kind of silly if we are all meant to be a family. i do not know if i am overreacting or if it is plain obvious that someone is overly competitive in a kind of weird way. to note she is not engaged to his brother but they live together. what should i do? if i mention this to my fiance his answer is that i should disregard it (as she sends the same pics to his parents too) but i do not think it is innocent on her part. she was very unfriendly to me when i got engaged and also told me openly that she will never be my friend and that i do not matter to them. she also said to me that marriage does not matter to her so the fact i am getting married means nothing - quite opposite it is obvious to all us she is desperate to nail down his brother as she left her job, country and everything to be with his brother. i am unequipped dealing with bitchy comments and bitchy behaviour and it made me very unhappy in the past. help?