Ask her what kind of soap/perfume/shower gel does she use and if she gets confused, name one of your favorite brands. if she answers with whatever tell her to stop using those cause they seem a bit weak and not doing their job.
More upfront way about it though: Just ask her out for a cup of coffee and tell her: 'I don't know how to tell you this, and please don't take this as an attack, but you/your clothes sort of reek? I'm telling you this as a friend so you can do something about it :x'
Be like, "Sis, I love you, but being around you makes me nauseous. Idk if you take showers regularly or if you have done stinky condition or something, but...you smell."
I mean if other people have straight up told her and she hasn't done anything about maybe she is against showering or something.I would just learn to live with it, you can't make a person shower and unless they work with costumers I don't think management could do anything about it but you could always try telling them.
