Agree, @FeelingSadToday1 .
There are many more role models than there were years ago. I held back from posting along the lines of You can live happily with this problem, even if it persists and is severe because, as FeelingSad says, it is difficult to hear these things when you are at a stage where your daughter may well turn out just to have a passing and minor bout of alopecia.
But in case it does turn out to be a persisting problem, I'll just mention that I have had alopecia now since I was 12. In my early to mid teens it was severe patchy alopecia, coming and going rapidly. Then, in late teens until about 50 it was relatively mild and maneagable. I took a dive into alopecia universalis from about age 50.
I survived!
The worst time was the first couple of years. But this was at a time when schools didn't think it was their job to prevent bullying! It was also a time when no women at all were out and proud with hairloss.
I think there are more options now. Many girls have a much more 'curated' appearance, so if you do happen to be a family that is into beauty management you may find much more potential for wig-wearing and other cosmetic interventions to be a positive experience (if it comes to that).
But, crucially, if your daughter isn't one of these girls who are into all that, please do consider the possibility of a short haircut that does not attempt to cover the patches. During my teen years, I was obsessed with covering them up as far as possible, letting the hair grow longer so that I could use hair grips to pull it over the patches. But all that bother just reinforced the idea that they had to be hidden, which they don't.
With alopecia, short hair feels stronger, cleaner, more manageable, less demanding. Kids at school will be interested for a while and then get used to it. If any child is unkind, teachers will take that seriously. All will be well!!