I wasn't invited to a birthday party?

I just heard that one of my friends was having a birthday party for two people that I've known from high school from my younger sister yesterday. I was asking her when she was going to have the party. I asked her if I can come, and she said that I couldn't come, because I didn't get an invitation. She got invited So earlier I was begging my sister to take me to the party and she kept saying no, and I kept asking and asking and asking and asking and she finally said that they didn't want me to come to the party because I was annoying as hell and I would annoy the hell out of them if I came and they didn't want her to bring me. I was hurt and astonished! So I pulled on my sister and I was begging and begging and crying and she said, "LET ME GO, DANA!" and ran off! They didn't want me to come?! I'm crying right now! How could they?!