Hi- You'll just have to swallow your fear and tell her. Before you do, you might want to give her a gift of some sort...like fancy bath salts or cologne, etc. Tell her how much you care for her. Tell her that you feel so close to her, that you trust her opinion. Then....tell her. Just say something like, "Y'know, this has bothered me. At first I thought it was ME. But I know I would want you to tell me if there was something you noticed about me. I love you". Maybe forget the gift, but just be honest with her. That's what friends are for.
Joke around with her. If you say it seriously and politely she'll still take it as an insult. Trust me, I've been there. Joke around, be like: "you gotta get some dove and Victoria body mist around...you'll smell like a butterfly!" Or something like that. I'm really bad at joking but if that helps.... Than oh well, good luck!
My husband and I have been married now 8 yrs and I just tell him. If she is really sensitive maybe buy her some really good smelling bath stuff. Perfume would prob just make it worse. She needs to shower every day or after workouts.
No matter what you say to her she's going to be either hurt or offended, how about buying her some really nice soap or shampoo, hopefully she'll take the hint, if not your just going to have to tell her straight up, baby you need to take a bath!!
Well this puts another meaning to "breaking it to her gently". :P
If it was me, I'd make it a point to bathe WITH HER regularly (if that's your thing that is). Wash that particular body part of hers. SMELL it, like put your face on that part and tell her how nice it smells. This should make her more conscious about that body part and see if she's taking care of it enough. She'll notice it enough that she'd take care of it from then on. That's how I'd approach it, with POSITIVE REINFORCEMENT! :P
Easy: Go to bath and body works and buy her a whole bunch of stuff as a gift. Give it to her and show how excited you are for her to use it, she won't be offended because every girl loves bath and body works.