IMO asking her to take a shower could save the punt - it would depend on the way you ask.
Don't doubt it would be very awkward for many punters, it depends partly on what attitude you have to it. Personally I think a bad smell is not necessarily the result of bad hygiene, it can come from chemical processes the lass can't control, in which case it's not something to be embarrassed about.
I've only encountered it once in 3 decades of being sexually active - with a GF who normally smells lovely. One time after a drunken night out she fell asleep before I could fuck her. She woke up wanting sex, didn't notice much smell at first, but when she knelt up for doggy it was over powering, I couldn't enjoy sex at all.
This is the sort of wording I'd use if it happened on a punt:
"Babe, this is a little sensitive but it's worth saying. With most women, every once in a blue moon their PH goes out of balance, and even though they have good hygiene. It's nothing to be embarrassed about, but I think it's happened to you. Would you mind taking a shower please?"
* Yes I know some WG's dont like being called 'babe', but I don't tend to punt that sort.
** Also know in this scenario it does at least slightly imply bad hygiene, as unlike with morning gf sex she should have took a good shower first. Often good to be diplomatic about these things.
Once she's out of the shower, if she seemed to be at all ashamed about it, I'd probably give her a quick spanking to take away any feeling of guilt.
(I've done this when lasses have been embarrassed about other bodily things, like a fanny fart, it's always been appreciated so far.)
When it comes to a bad smell, I've not actually done this on a punt as its never happened to me. But fairly confident it would work, I'm the sort who does have a quiet word when I see someone with an "embarrassing" condition they don't seem aware of, and so far it's always seemed to go down well...