My Boston Terrier is regressing on her potty training...what should I do?

K, my Boston Terrier is 3 1/2 years old. Since she was a tiny little puppy she has always asked outside to go potty. Just recently I started noticing that her bed in the laundry room was wet. I realized she has been urinating in her bed. I ama stounded; she's never done this. The vet checked her out for bladder problems- nothing. Perfect health. If I put her in the laundry room when we have guest she pees on the floor (I'm guessing she doesn't like it there anymore). But when I let her come sleep by the fireplace she decides she wants to sleep on my chair; when I tell ehr "no" she goes and pees on her bed by the fireplace then tries to hide it. I get it. She's mad she can't have it all her way. But how do I fix it?