(photo) looking for help identifying an issue

[amildiaz]

Is this just a case of vent gleet? How can I be sure?

 

[amildiaz]

Here are another couple photos where you can see how swollen she is below her vent. It kinda of looks like there's a bulge down there.

 

[coach723]

It looks like dried droppings to me. How old is she? Is she laying? Is she acting normally?
Dirty butts can be nothing to worry about, it happens. If it's a constant thing then it's good to rule things out that you can. Older birds may not push droppings out as hard which can lead to dirty rears. Internal parasites, diet changes, or drinking lots of water when it's hot can lead to runny droppings and dirty butts. Sometimes reproductive problems can make it harder for them to push droppings out and that can result in dirty butts. A bloated belly is also often an indication of a reproductive problem, a cancer, an infection, internal laying, organ failure. Does it feel water balloon like, or very firm? I would clean her up, trim feathers under the vent if needed to keep droppings from sticking. When it builds up then there is a risk of flystrike (flies lay eggs in the droppings, they hatch, and the larvae/maggots will eat the bird) so you want to prevent that.