Why do you feel like you have to tell her in the first place?
It doesn’t sound like you’re close enough with her to tell her straight up, so why are you interfering in her life?
Don’t get me wrong, I hate the fact that there is another fauxtog in the making. But why not let her learn for herself? Let her get low-paying clients, and let her deliver unsatisfactory photos. She won’t last long unless she gets good. And if she does happen to get good, who are you to have wanted to stand in the way?