I'd first double check around your house to make sure she isn't going anywhere else (I thought my cat had stopped peeing one day, but then found a messed towel in the corner of a closest), other than that my only advice is maybe try mixing a little of the pine sawdust in with her litter, just so it has the smell of it, and see if that encourages her to use it again.
"I'm in your vagina, lurkin on your garlics!" - paprikapapaya
"My vagina won't even come to the table because she's out fighting crime under the name The Pink Boom." - idatetattooedguys