To add to the good advice above it could be pain or having gotten a shock by something and unfortunately she's connected it with you!

If she suddenly experienced a sharp pain in her hip, for example, when you sat down with her then she very well might associate YOU with the pain. I would advise a vet check (which you are already doing ) and then some exercises to associate you with good things... Not forcing her to interact with you but more 'enticing' her

Good luck