My sister doesn't want me to date? Any advice?

Anonymous
So recently I was asked out by this girl who is in my physics class. We'd known each other for a while, and I'm very introverted so I accepted. I was curious more then anything.

I was telling my twin sister about this, and she wasn't happy with it. She said that she thought we should wait until were older to date, after 18. (We are 15 now). She said that it was really pointless and I should focus on school. She also said that she didn't want me to be spending all my time with some other girl (she'd get lonely).

I'm really conflicted about this whole situation. My sister and I are really close (we're twins), and so I'm leaning towards agreeing not to date for a while. I want her to be happy. But I still really would like to for the experience. I really don't know.

I really appreciate any opinions on what I should do!
Updates
+1 y
I feel like I'm betraying her if I keep dating.
My sister doesn't want me to date? Any advice?
6 Opinion