Before I even got to the end of your post autism sprung to mind. I'm not sure what the process to have them assesed these days is as mine went through it 21 years ago, but I think your on the right lines.

Poor Jasmin, its not fair of her parents to lay that kind of responsibility on her. Life at home cannot revolve around the child with special needs or they'll simply end up with two children with special needs. Advice them to contact social services to find out what support is available to them but from experience my advice is if theres an offer of childcare give it to the special needs child and spend time with the other.

Speak to the parent about your concerns of austistic spectrum issues. The parent needs to speak to the health visitor or doctor. There will be help and support available.
You sound like a very understanding grandparent.... please carry on being like that. Maybe, you could have both children, individually, so that the mother can spend one to one time with each child.
Your grandchildren are lucky to have you.