Take care of it on her own

The hornier she was the less she minded how slimy her pussy was feeling, her mind too busy trying to deal with the need for dick to care about the "water" possibly seeping into her precious place and missing how much was gushing inside due to it... obviously the more sperm wriggled its way up her cunt and into her womb the more stimulated she was, further arousing her body and possibly leading to an orgasm given enough time.

Mei knew nothing about it, just feeling unexplained pleasure and trying her best to not show how much this dirty swamp was affecting her... blissed ignorance!
Her womb was already soaked in hyperactive semen, any ovum in there was pretty much doomed and all their wriggling around was genetically designed to stimulate further ovulation... and yet she was still worring about Ren knowing this dirty water got her hot!
But denying it was useless, and if anything she could even start to feel pleasure just by walking forward... hell, even when she stopped she could still feel good!

It was like the swamp was alive and caressing every inch of her body, inside and out.
The pleasure kept growing, and eventually Mei gave in to temptation. Most of her body was hidden by the white waters, too murky to see what was going on below, not even how one of her hands found its way between her legs, caressing her kitty through her panties... her other hand quickly went to cover her mouth, last she vocalized the pleasure she felt.

Luckily Ren was in the lead, and he wouldn't notice if she slowed down or acted strange as long as she wouldn't give him a reason to turn around...
And so her walking speed slowed, the girl even spreading her legs a bit as she rubbed herself down here in an attempt to reach her peak and be done with it before reaching the other shore and possibly without Ren noticing what was happening... the thrill of jilling herself without Ren finding out, the risk of him turning around and noticing something he shouldn't, this dirty swamp still affecting her so much...

The lust had gone to her head, and she was now thinking with her pussy rather than her brain.
Eventually she even slid her panties aside, removing the only filter limiting the amount of lizard spunk seeping through!
Useless to say, if Mei was in her right mind she'd feel the "water current" get restless and gushing into her most precious place... but she wasn't, instead welcoming the added pleasure as she slipped one of her fingers in to jill herself.

With no more panties in the way and Mei's finger rolling around... more and more semen could get inside, Mei's fingering even pushing the cum deeper and helping the inseminating effort of those swimmers.
Her pleasure peaked, and Mei barely managed to restrain herself from crying out as she squirted, her love juices attracting even more wrigglers...

By the time the waters got shallow enough for her belly to emerge, she orgasmed more than a few times and her previously flat belly was now swelling from the sheer amount of cum packed in there... it wasn't noticeable thanks to her clothes, though Mei still felt quite bloated. Was it because she touched herself in those murky waters? Was it unsanitary to directly expose her pussy to the dirty bacteria in there?
Little did she know... exposed? Her belly was full of those "bacteria", and even her eggs had "caught the bug"... the kind that'd leave common women "sick" for nine months!

Well, for sperm lizards it'd take just nine days to come out common women... but she wasn't a common woman, she cultivated the Fertile Matrix Fecund Body Cultivation Technique and that's mean it'll take much less than nine days for Mei to pop a few lizardmen babies out.

Actually, it may even take just a nine hours or so.
Even in the Yin-Yang Heavenly Pavillion few knew that the Fertile Matrix Fecund Body was a technique of demonic origin redesigned to fit their need... usually, among other things, it'd passively speed up pregnancy and the cultivator could choose to use more of her energy to further speed up the gestation.
However, when mating with a demon the real side effects of the technique would show... sure, those swimmers wriggling were designed to make a woman's ovulate, but the reason her ovums popped out so easily was due to this refining technique!

And now that she got a few lizard buns in her oven, the technique wouldn't just passively fed them her energy but actively drain it to maximise their growth!
She had no control over it or would even notice, at least not anytime soon... while there was still some tingling down here, she jilled herself to satisfaction and was now basking in her bliss, ready to kick some demon asses!

[Mei Qi drained by 5]