If she didn't shower beforehand or if she did but did not wash her nether regions well, then you can ask her to wash up first...this request will force her to think a moment and tell you 'next time' as she also doesn't want to interrupt the fun.
If she did shower, then tell her you only daty with a dental dam (plastic wrap will do too)...then she will herself stop giving you a bbbj and offer a cbj instead.
Your choices in the end are to just literally suck it up and go daty her. If you don't want to smell her, then mash your nose on her clit so you cannot smell.
Or tell her to stop the bbbj/cbj as you are gone to cum very soon, then immediately go to the shag. In this way, face is maintained for all parties.
I personally would go on to the DATY. I don't mind a weak fishy smell as I gonna to try to make her want me to DFK her after getting her to cum hard. As she taste/smell my tongue, she will know to eat a better diet for next time.