How to tell someone they smell? (politely)

This is NOT a racist/troll post yall, im Indian myself.

Basically..theres this girl in my class, she has horrible BO, like, really bad BO, I know this because I can literally smell it if I sit shoulder to shoulder next to her on my seat…she doesnt even have to raise her arms fully.

I casually asked her how often she showers, and she told me she showers twice every day, so this is not an issue of not showering, I believe she has some sort of condition which makes her sweat so much because our classrooms are well conditioned and no one else has that smell on them… I want to suggest she uses deodorant, but at the same time I dont want to come off as mean, the girls in my class often complain that my perfume and deodorant makes it difficult to sit next to me (I tend to apply too much as I stay out of home for almost 10 hours) and I dont want to make it seem like im judging her for not using as much product on my body as I do, whenever I talk about my skincare routine, the girls in my class, including her often roll their eyes at me because they think I show off.

Anyways, how do I casually tell her that she should do something about her BO in a way which doesn’t make me sound like a jackass?