My Sasha had a similar story when I adopted her 10 years ago. She is a border collie/healer cross. She would drop to the ground every time you approached her. She would not catch, not even food. She'd just close her eyes at let it hit her. 10 years of love and attention have turned her into a goofy, silly, happy dog that will now catch treats and pretend she's a lap dog. It took about a year for her to stop the drop as you approach move.

Patience, love and tenderness is what you new baby needs. I hope it doesn't take her long to get comfy with you and begin to enjoy her new life.