Hello. Glad you have joined us, and I am so sorry your sweet little girl is having all these health problems, and it has been such a cost and worry without a resolution as yet for you. How old is she? Is she very young? I'm also sorry to hear she had wet tail, and it's good she survived that. Presumably she had antibiotics for that. After a lot of antibiotics, a hamster specific probiotic can help line the get. I'll come back to that later, but I don't think it's the full answer.
If she is coming out, eating and drinking and going back to bed, how does she seem when she comes out? Does she seem unwell and lethargic? (I think you mentioned that). Just ruling out her hiding away/versus feeling unwell?
My first though was if it could be pyometra, as she's a female syrian. There are two forms - open pyometra or closed pyometra. If it was open pyometra I think you'd know as there would be a discharge (perhaps the wetness?) but it would smell foul as well. If it's closed pyometra, there is no sign except sudden extreme illness that needs urgent antibiotics. Maybe your vet has already ruled this out.
Diabetes - while it's common on russian dwarf hamsters - campbells and hybrids, it's not common in Syrian hamsters - quite rare but possible. You can test for sugar in the urine yourself to see if it's that or not. You can get ketodiastix from a pharmacy or on amazon - these are for human diabetics but do the same job for hamsters. Dipping the stick in urine, it shows if there is sugar in the urine or not.
It could help to rule it out, but I wouldn't stress her trying to get a urine sample if she's unwell. It seems unlikely to me and if she's unwell she needs to avoid stress.
It could be she is just taking time to recover from the wet tail or other infection, or has some pain. So without a clear diagnosis, I'd try a probiotic and maybe give a pinch of shelled hemp seeds daily, separate from her main food - eg on a little jar lid. Hamsters seem to like them and just lick them up - they are natural way to have a boost of vitamins and minerals as they are full of them, so a good immune booster. Brazil nuts also contain something that is immune boosting, so you could break one up and maybe give her a quarter piece a couple of times a week. Half a brazil nut is a bit large and could be a choking risk if she;'s unwell. Or you could crush half a one and put that on the separate little jar lid with the hemp seeds - one each side.
I would consider asking the vet for some loxicom as well - pain relief. Just to see if that helps in case she has any pain.
Also is your vet an exotic vet? Exotic vets know a lot more about hamsters than general vets. If she still has wetness around the rear end it's possible she either hasn't fully got over the wet tail, or it might be pyometra. Is she on antibiotics at the moment?
I can't recommend a suitable probiotic as they seem very hard to find for hamsters these days - the benebac powder for small animals used to be one of the best, and one that vets in the US used to prescribe (I think you're in the US?), but it seems unavailable these days and the gel version in the syringe is too high a dose and not possible to get a small enough dose for a hamster. So it could be worth asking your vet for a probiotic.
There is also Emeraid Intensive Care Omnivore which is supposed to be very helpful for unwell small animals - however, I wouldn't give this without ruling out diabetes first, as it's high in sugars and could make things worse if a hamster has diabetes. The link below is for Amazon uk - I'm not sure where it's available in the US - it might need to be vet prescribed.
I also think it would help to know what's going on first. The way some people get a urine sample is pop the hamster in an empty pet carrier for a while until they do a wee. It rolls around on the plastic base so easy to dip the stick into. But I'd be concerned it would cause her additional stress which won't help her immune system and it's unlikely to be diabetes. I think it's more likely to be after effects of the wet tail or reproductive possibly.
I'll wait until we hear back from you to see how old she is and if she's on antibiotics at the moment, before suggesting anything else, because the antibiotics themselves can sometimes make them seem unwell.
Emeraid Omnivore