dear colleague,

How about using touch..... ( give a massage and teach her parents to massage her)
Let this child feel that you are a loving caring person that wants to help them... not stick needles in them (just an example)
a few ideas are:
1.Give a lot of sensory information and support. The trick is to find positions in which you can entice her to move, to touch something or lift her legs. Do this in a good supported position, not in cushions, but with a firm support. It is easier to start moving with firm support than from soft moving support such as soft cushions.
2.Put her on a slope ( supine or prone) and let her "feel" the effects of weight change and gravity......I prefer a slope to the ball, the ball is too unstable. You can do so much... changing het environment to fascilitate moving is one of the easiest.
3.Use your ( or parents ) lap, balancing her on a leg, close to the ground to help her move.
4. Gentle move her passively a few times ( example roll from side to side)... then wait, see if she reacts and wants more and wait for her to respond.....

One of the things to keep in mind is that children with developmental delays need a lot more time TO REACT... so please give them that time.......

Hope this helps a bit.... good luck to you both

Esther