Whatever you think is cleared up now, it hasn't. It'll come back to haunt you again.
Prepare yourself for this:
She will talk. Then her friends will talk. If she's really butt ugly like you said, she's probably proud to have scored with you. And she'll talk once she's gotten over you. Eventually, your sis and your friends will find out.
You had better have something nice to say then, and not break her heart twice by slagging her. It will be terrible to disrespect her again.