How old is she and is she spayed? Let us know......
If she hasn't been spayed, and she looks at ALL unwell....even if her symptoms are subtle, such as drinking more water, or sleeping a bit more, then get her to the vet as soon as possible. Just in case this could be Pyometra, which is very serious and needs urgent treatment.
If she has been spayed, and doesn't look so bad in herself, then it could possibly be a bladder infection, or mild vaginitis. But it is possible -even in spayed females- to develop what is known as"stump Pyometra". This is quite rare, but can happen.
I think you should take her to the vet -just to be on the safe side- it's always good to take vaginal discharges seriously, in case of possible Pyometra.
No she's not spayed and she's 7yrs old