11 year old rescue peeing her bed

Question
We brought home a 11 year old Beagle from someone who did not have the time to give her the attention she needs. We have a 4 year old cat, that behaves more like a dog. They have been slowly getting to know each other, a lot of sniffing each other and a couple of hisses. The dog was great with bathroom breaks for 3 days, then we caught her peeing on her bed. We just acted like nothing happened and cleaned up the mess. Since than we bought a second bed for the bedroom at night. last night she pee'd  on the original again so we brought the other one out to the same spot and today she pee'd on it twice (the new one). what can we do to help correct this?
Also, the last time she pee'd, she had just came in from a unsuccessful walk.

Answer
first,sorry for the delay in answering the question-my internet server has been down.

I think the best way to deal with this,would be to crate her at night,while she might want to go on your bed she won't want to go on her own,but if she does go at least it will be contained.And do that for about three weeks,then start leaving the crate open at night. Also reducing water intake for an hour before going to bed also helps

Also,due to her age,you might want to get her checked out by the vet to rule out any medical problems