She sounds ungrateful. :/

Umm, does it bother anyone that the persons name is "onlychild" but said they have a sister? I just think it's funny. Funny story tho ✌️

She's just going to embarrass herself in front of everyone that knows she actually does have a sister if she says that. Even if she doesn't like you, let her know that and suggest simply saying the friend was like a sister to her, without adding "that I never had".

Give her Haribo sugar free gummy bears on the day of her speech.

Well your username is kind of contradictory

Reflect back on your time with your sister. Either it's a false lie, or you really weren't there as much as her best friend. Hopefully you'll confront her and find it out.

im sure it was only a mixup :)

OP here! After reading some of the replies to this I have to clear up some things I think. My sister and I have 7 years between us, me being the oldest. So, about the time I was entering college and moving out, she was entering middle school. This did create some more distance between us as we were not very close to begin with, I'm sure age had something to do with that. However, I have always been very supportive where her education is concerned and she's always come to me with problems, especially those you don't want to talk to mom about. I can tell you for sure that neither one of us is adopted, we are however half-sisters, but I really don't think that makes much of a difference in this case. I'm not sure why it was written and she won't change it. Our father thinks it very hilarious and what can I do? Sometimes she's just odd, though I love her very much. It might be an awkward graduation moment though, I'll be sure to have the camera rolling :)

Why does your user name say only child lol

gotta love sisterly love!