3 methods:
1. "Hello, HR? Can you tell <name> that she's wearing too much perfume? Thanks."
2. Get a female coworker to say to her, "a couple people mentioned that your perfume is a little strong..."
3. Tell her, "I don't know how to say this; but I don't like to talk behind people's backs. A bunch of other people in the office have been commenting that your perfume is too strong. It really doesn't bother me, but I just thought you'd want to know, since I don't think anyone has approached you about it."
4. "Hey, what brand is that?" . . . "I can always tell when someone's wearing a real name brand perfume, and not a copycat - the smell is so much stronger and lasts much longer."