I'm so sorry to hear about Emma! She is so lovely and it's awful to hear about what she may have gone through (hit by car or injured by a person). It sounds like she is in alot of discomfort and I will certainly pray for her that she will begin to use the litterbox on her own.
Is there anyway to put her by herself in a bedroom with a tv so she has some background noise going so it isn't so lonely for her? Or in a bedroom where other people can keep her company? It sounds like she is so affectionate and maybe 'being' with her family or in an environment that is more normal might inspire her to relax and 'go' if she is able to. Just a thought. Prayers and hugs going out for Emma.