Maine Coon kittens & cats in Waveland, Mississippi

We are a home with 3 rescue cats, of which Aster is one of them. She gets along with the cats and our purebred dogs (yorkie and lab). In the last nine months, Aster has started urinating in corners, in the bathroom, etc. We keep 4 clean litter boxes. We place a puppy pad where she urinates and continues to urinate on it. We do not want to bring her to a shelter. She is a loving, beautiful, fat cat. We were told she was a momma cat when she was adopted six years ago. She had a litter, and then she was a momma to another litter. I have spoken to a vet tech, and she believes she is doing this because she is mad. Our son has a rescued male cat, and I have noticed her watching him and ready to engage. While I don't believe she will hurt him or anyone, she appears to be acting out because she isn't happy with this new boy cat. We do not know where else to turn. Yes, there is no doubt we will miss her when she is rehomed. Can you please take her in?