My mom hasn't spoken to me in a year and 1/2.....?

because of a fall out between me and my sister. She chooses to side with my sister rather than helping us forgive each other. I really miss my mom even though she's shuned me (which has happened on more than 1 occion) So much time has elapsed that I would feel foolish to even step forward. She's played this game before on me but it's never lasted this long. Why would a mother do this to her own daughter. I feel so unloved and abandoned. With my father having ped and my only other sibling living so far I don't even feel like I have family. I'm really sad. What do you make of this.