I'm expecting something like that.
They should as its a normal biological function. Or I should say, shedding of the uterine wall should still continue, given how we've seen the slime-blood reacts to damage she wouldn't bleed. Our slime found Lady Jelly's body when it was still fresh and cellular death hadn't occurred. The slime replaced Lady Jelly's blood, delivering oxygen and nutrients to keep her cells alive and continuing biological processes. Thus Lady Jelly's uterus would continue normal biological function.
With a few caveats. Uterus changes would be triggered by hormonal changes, and thus it require glandular function in Lady Jelly's brain to continue, and we're not given a good gauge on how much of Lady Jelly's brain is still there. I would think her thalamus is still intact and functional because she must still be breathing for two reasons:
1) No one has called her out on not breathing
2) while I'd believe the slimefluid can deliver nutrients to the cells I don't think without aid from lungs it would be able to pull in enough oxygen to keep Lady Jelly's body alive.
So I think Lady Jelly is just effectively in a coma, with an inteact lower brain just no cortex activity. Thus her uterus would continue its monthly cycle. This also means when she and Hero-kun get married, she can have his completely normal full human children.
Thank you for coming to my TED talk on "Overthinking biological and reproductive processes in a silly comfy gag manga"
Now here's the real brain boiler:
Slimes dissolve everything organic and don't really excrete any waste. But human bodies do.
So Does she poop?
The brain must be mostly, if not wholly intact. We've seen Jelly recalling past memories from when the original was still alive, though not all of the memories are perfectly preserved. Though that might just be evil jelly not remembering or caring enough about older things.
Plus, I'm thinking there is something more than just controlling a brain dead body. Iirc Jelly was told that the fusion is permanent, theres also how she cant be detected as a monster by magic means like what the Hero uses. Then there is how she passed out and regained consciousness after taking full control of the body.
A quick theory of mine is that Evil Jelly is dead, gone. Her soul had left the body and moved on. Slime Jelly found it and moved in. Like a hermit crab donning a new shell. Like moving into a previously abandoned house, she patched up the damage and settled in, essentially becoming one new entity.
Now theres also how quickly she got used to the body and all the changes. Especially for someone as... dumb as her lmao, slime Jelly definitely had some divine help. I bet the Goddess was thinking this bitch is a lost cause and decided to let the monster have a go at it.
Slime turned out to be of pure soul and goddess started protecting her.
Also most importantly: she probably poops. Given her new body she cant use all the nutrients as efficiently as before. There's only so much blood that can fit inside a body after all, waste must be extreted. Though she most likely can utilize far more of her food and survive on a far smaller diet, given the amounts her gluttonous self consumes she must have to poo.