This, OP.
You may not know, but this poster ^^ has been involved in education for years, and is a child safeguarding expert.
Tell your daughter that the children there who shouted over her have been indoctrinated. I know it sounds a bit mad, but there it is. When you have rapists being sent to female prisons and men taking women's awards in sporting events, we have to accept that indoctrination is exactly what it is.
And that bloody adults, all of whom should know better, have been influenced to the extent that women have had to go to court to make sure the law is upheld.
And because of those women your daughter's views and actions are now legally protected. The event organisers were guilty of discrimination by their actions. And, by classifying those views as hate, very likely defamation.
In fact, the whole bloody event sounds a little bit like a spot of indoctrination if you ask me. Let's hear your views, and we'll classify them according to our own prejudice.
Your brave daughter is totally in the right. And it takes some bloody balls (as it were), to stand up for what you believe, in the teeth of peer pressure.
I don't know about her, but when I was at school long time ago, we were taught about peer pressure and how to withstand it. And now adults appear to be complicit in it. Shame on them.
It's bloody awful that she's now been made to feel afraid.