Why is my spayed 15-year-old cat acting like she’s in heat?

Dear Most Esteemed and Knowledgeable Kitties:
I have a cat that is 15 years old. I had her spayed 12 years ago. Right now, she has been in heat constantly for the past 2 months. She also has been urinating all over the house, mostly on my husband’s things. She has also been drinking a lot [...]