Gee... HERE I go again. The cat may be simply trying to piss off the dog by getting on her bed. Now, it COULD be he is trying to be friendly to her, but that just don't add up in my mind at this point.
Has she tried petting the cat when he does this? Now, THAT might piss off the dog but I don't think the dog would attack the cat over it as long as she makes sure the dog is reassured of her committment to him through the day. Not TOOOO much petting, just a wee wee bit and no vocalization.