my friend thinks she's ugly

So my friend says that she's ugly. So I tell her that no one thinks she's ugly. And then she said bet and so I said I'll ask a bunch of people what they think. I sent a snap to about 20 of 25 people because those are my only snap contacts that know her from school. And 14 people opened it so far and said she's not ugly. She said they were lying, but honestly she's pretty. Any advice on what to say to her or any advice for her. I mean I'm insecure too but I don't call myself ugly. And plus (forgot to add) some boys said she wasn't ugly either but this guy she likes only likes her as a friend and she's convinced it's cuz she's ugly. She 13 years old.