remember that poeple can change. some of my friends had friends that i really couldnt stand, but i thought to myself 'if i can put up with this person, and be happy around them, then it will probably widen my threshold to put up with other annoying people throughout life'. i know it may sound harsh, but it worked. and before i knew, i had learnt to adapt to the person personality, and i got used to it. plus the person changed alot as well while i was getting used to his personality, so in turn, things worked out for the best.
id just say, try to put up with her. if all of your friends dont like her, apart from your best friend, then maybe your best friend will realise.
buona fortuna