It's a phase she's going through. Miley is now a teenager and is showing her 'independence', just like human teenagers
"Yikes sit on Mom's lap? No WAY".
Don't try to push her, just allow her to come back on your lap, which she will sooner or later. If you don't take any notice of her when she's lays on her bed or under the couch, she'll soon realize that it's just grand to sit on Mom's lap and get heaps of love and attention. Being ignored isn't really what she wants at all so ignore her when she's sitting elsewhere
My boy, much bigger and definitely not supposed to be a lap dog, by breed anyway, always loved to sit on my lap, then went through a phase of not wanting too, now he's back BIGGER than ever on my lap