My autistic sister's blankie is falling apart. What should I do?

So, my sister is autistic and she has a Marks and Spencer nightie that my mother gave her to use as a blankie when she was a toddler. It is now many years old and falling apart. I bought her a new and different blankie, but she says she doesn't like it much because its not the same. She doesn't use the replacement and is still using the old one. But, it is continuing to fall apart and I am worried it will soon be a pile of rags which she will be unable to use. She is going through a tough time right now. She is suffering with a lot of health issues, and it is all causing her so much stress. The blankie gives her quite a bit of comfort and eases her stress. I am worried if her blankie does fall apart completely she will have a meltdown and be completely unable to cope with anything. I know this is a long shot but....Does anyone have any ideas on what to do? Does anyone know if it's reparable? Does anyone know where I might find another one?

Here is a picture of it.