I'm sorry that I don't have anything useful to contribute. I had no idea what was really going on with your sister and I feel very sorry for you and her. I really hope you can find a solution that works at least as well as what you had before.
Googling for a while did lead me to this:
Voice Activated Call Systems Help Residents with Physical Limitations
Scroll down to the headline "Physically Impossible".
They even mention MS.