My sister (14 F) asked me (19 M), if she could have some chocolate. After much deliberation, I in my graciousness said yes, and she responded most rudely with an "ahhh yes" like she had won a personal victory. Therefore, i due to her ungratefulness, said no, which resulted in much begging, and eventually i caved to get her to shut up.

HOWEVER, she did not thank me as she should but responded again with an "ahhhh yes". She then started laughing and has apologised but due to her original hubris's and response to her attitude prior I have decided to not yet give her chocolate due to this incident and have stopped her from stealing it as well.

This brings me to my question am i an asshole and just give her chocolate or am i justified in my response?

edit: this is my easter chocolate, she's already had hers.
edit: i've already given her my easter chocolate before