Dog peeing on her bed and blankets

[angeluv24]

I just recently rescued a female dog of probably 4 years old that was an outside dog for the past 2 years, but before that was an inside dog. She pees on her bed during the night, but has also peed on her blanket that is on the couch right in front of us. She is house trained as she never has "#2" accidents inside. I take her out and praise her when she pees outside, I wash her bedding after her accidents, but this is a behavior that has gone on for a long time, and my question is, of course, HOW do I stop it?! She's a sweet little dog and I don't want to put her outside (it gets -30 in the winter here and she is 13 lbs and doesn't have much hair!!!) because of this!
Thank you for your help, I'm new here and hope I'm doing this right!
Angela