Dawn has always said she loves Billy because he's the father of her children. I do think she's led Billy on for ages. Lots of arm rubbing and little looks. Keeping him on the back burner in case it all goes wrong with Joe. That's why she didn't like Billy moving on with Gabby. So I don't think it's come out of the blue. I think she just got bored with Billy and liked the idea of being lady if the manor at Home Farm. Plus Joe pursued Dawn relentlessly. Her and Billy have always had a laugh together which she never has done with Joe.