My cat pee's

if we leave a towel on the floor or clothing she'll pee on it. Why does she do this...she's always done this and she's now 8yrs old or so. Its very much a pain in the butt....and I get so angry at her that I've threatened to take her to the Humane Society. I'm forever looking around the house before I leave to make sure there's nothing for her to pee on before I leave for work and then I run around after work doing a check.
She also eats plastic bags and I have another cat who licks the walls, I swear my animals are retarded...LOL
Any ideas?
Maggie

Take her to the vet to rule out a Urinary Tract Infection. That's one of the signs, since they can't speak. Is she spayed??

Plastic bags contain fish oils which attracts cats since they love fish. Not sure why the thing about the walls. Might want to ask your vet.