cat pees in dog baskets

Hi!

Ive got a 2 year old cat since 15 days now. The first week she used both litterboxes and she still does, but since 5 days she pees in my dogbaskets as well.Once a day... I dont understand this. Why was she all clean the first week and started doing this now?
I cant wash these big foam baskets with pluche,had to buy 2 new ones,cost a lot of money and again,within an hour she peed in the new ones as well.

She doesnt act stressed at all and feels at home much more than the first week,is not afraid of the dogs,has lots of places to sleep,litterboxes are clean...can someone please tell me what to do about this problem? I would hate to give her away again but im a pensioner and havent got the money to keep on buying baskets for my dogs. As they are eldery dogs they need a basket,cant have them sleep on the cold floor can i?

Thanks for any tips,
Marion