I think that you can, very kindly, tell her the truth. You have to separate, in your mind, saying something that you know she won't like hearing, at the time, from thinking that being honest with her is mean because she won't like hearing it. It's much kinder, in the long run, to tell her the truth, so that she has the choice to modify her behaviour for her future. It takes courage but, I promise you, you will feel better for taking the courageous path, because one of the things you are scared of, is her reaction. Try to put that aside. You can say it gently and with much love, but, no doubt, it will still be embarrassing and difficult for her to hear. Love is sometimes a little bit brutally honest, for the long term good of a person. So, I say, get it all off your chest, don't try to hide an uncomfortable truth from her, that's treating her like she's too fragile to be honest with, give her the benefit of the doubt, lay it all out there so she can benefit from your perspective and have all the story out. Then she can learn from her mistakes. It's the truly loving thing to do.