What should I say to her or how to approach the conversation 😟

So few weeks ago I met a girl at the festival I went to randomly and we hit it off besides our very similar personalities I think she is a real darling. Anyway that day I didn't think much of it because we have been dancing and it was a long day but She had a really strong body odour and not in a nice way. Very strong!!! I have been catching up with her regularly doing girly stuff and actually that's how she always smells. She stayed at my place few times and after shower I will offer her my deodorant and she will use it without saying no or hesitation. So I bought her one without saying anything as a present but don't know if she uses it or not .Last week we met up with my other friends and I saw their reaction to the Smell, although none said anything in her presence later on my other friend mentioned it to me and asked me to tell her to use deodorant or something. I know this girl showers and she wears perfume but still the odour is very strong. So strong that everyone notice. I hate the reaction I see sometimes from strangers when we are out. Somehow though she is oblivious to it. Today I am having lunch with her and I really want to say something but in a nice way and not just tell her but make sure she does something about it
Have you ever been in this situation? If so how did you handle it and did it work out?
Can it be a medical issue and she hasn't told me or don't know about? Should I just keep quiet ? Or what should I say? I really don't think she knows otherwise she would do something about it?
She looks immaculate always and well groomed is just the smell...Pffffff
Any advice would be very much appreciated ☺️
I really want to be her friend