Search Results: parents upset over my date

My little sister just turned 15, 2 weeks ago. She had a birthday party to celebrate and she wanted me to show up. I don't really get along with my parents but I made an effort to keep in contact with my sister through, Facebook, Kik, etc... On her birthday, my girlfriend wanted to go fishing. I explained to her that it was my little sister's birthday and that she wanted me to show up. My girlfriend told me there was no point in going if my parents were going to be there, because we don't along and she told me to just write a card. So, I explained to my sister why I couldn't come and she was upset but got over it. The week after, my sister got her first boyfriend (😑👊). She wanted to have a double date with me and my girlfriend, so that I could meet her boyfriend. I asked my girlfriend to come and she said, no because she just wanted to stay in and spend time with me. So, I explained to my sister that I couldn't make it and that's when she got mad at me. She told me that there was no point in keeping in contact with here, if i'm just gonna ignore everytime she wants to spend time with me. She won't talk to me or anything. I do feel bad, but I mean its my girlfriend.. I also don't want my sister to cut me out of her life. What am I supposed to do?