It is likely a urinary tract infection. Common ailment and can be treated quickly and inexpensively with antibiotics. It's painful and can eventually damage their kidneys, so you really need to get her to a vet.

Big Easy and Rivers Vet Urgent Care both do walk ins. You just have to get there early because it's first come, first serve. If you don't intend to keep her or care for her, surrender her at a shelter asap so she can see a vet because she is almost certainly sick and in pain.