I cannot tell you how to tell her, as in my case I was out since they were born, so "Daddy is a she" is something they grew up with.
I can offer you that as my daughters got to be teens, there were moments when they did suffer because of the gossip in the neighborhood and in the school. However, once we established the : "yes, my dad is transgender, and I love her just the way she is. If you have a problem with that, then take it with her," the "issue" went away, and now nobody cares or comments anymore.
While things were rough back there, I found that the youngest and smallest of my daughters had big moxy, she was my big defender going to blows with anybody who said anything about me. She is still pretty protective 🙂 My oldest boy and youngest boys are very quiet and very protective; my other son and my other daughters seem to be more or less indifferent to the whole thing.
Kids are very resilient, and if you love them and you are true to yourself, they would come for you