Hello Juanmi, my advise is as dre posted u need to think shes like a friend or your sisters friend and try to get used to being around her, oh and every time you are near her act like you are doing something that is really important and keeps you from looking at her. That way she'll notice you because if she's used to being looked at all the time by the boys and you are not doing it because you are always up to something she'll start to wonder and she'll be compelled to talk to you. Dont get me wrong and make the mistake of making her feel shes no there, Just that what you are doing is very interesting and hopefully she'll react to that. GOOD LUCK