This is a really hard one. Is there anyone you can verify nicely with that has also noticed the smell? If so that will help you be more accurate on how it affects others and frequency - this is data you need if you escalte.
Another issue is that some people detect odours on people that others don’t . Some of those are related to specific medical conditions that include diabetes (though most people can small that), kidney or liver diseases, and even schizophrenia - this I know personally as my exh had schizophrenia and before he was diagnosed acquired a very unpleasant odour that never went despite washing and showering well, trips to dentist, washing all his clothes in one massive hit. It wasn’t until he was being treated and crisis died down that the odour disappeared. Came back a few days before each crisis for over 29 years- but apparently only some people can detect this odour. Fascinating story out there of women who identified smell of Parkinson’s that Urey eventually developed a test for. So get verification from others to indicate if it’s something you’re especially sensitive too- which could well indicate one of these stranger chemical emission through skin pores that no washing or hygiene will help.
and many women , especially perimenopause, can be experiencing huge blood loss with menorrhagia, which a single form of protection won’t manage and needs a lot of layers of protection. It could be related to someone who is really really struggling with menorrhagia, or urinary incontinence etc.
So, for the women’s sake and dignity, try to find a female manager or HR rep- please don’t raise it with her male manager in case this is the case. It will be deeply humiliating for her and unlikely to get to what is actually causing it.
if it was BO, that can be associated with men or women, and is to do with with hygiene then , yep, I’d be more inclined to go to a male manager. But what you describe is more than that - please don’t humiliate her.
The obvious thing though, is to ask her for a quiet word in a closed room by yourselves. Tell her that you feel very embarrassed and nervous about having a discussion, as it involves a very sensitive personal matter. Explain you have, since she moved next to you, been noticing a persistent/intermittent (whichever) odour about her, and you want to make her aware of it. Apologise and say, obviously that’s a bit upsetting to hear , but reassure her you’ll not discuss it with anyone else. She’s unlikely to react well if she’s complexity unaware, so stay calm, don’t engage in argument if she starts back. Simply say “I’m making you aware of an issue and as I said I apologise for upsetting you. I don’t want to argue with you “ and leave the room. If she’s distressed and confused, reassure her, try to help her if asked to explain type of smell in less repulsive words than you’ve used here. Suggest if she asks for help that she starts with her GP.