Okay, so she started with these feelings when she was a teen. She is 58, so she has felt the desire to be in a wheelchair for 40 long years.
If this could be cured it would have been. If, in forty years, she hasn't been made to change her mind, and no drug can make her happy with what she has, then maybe she should have her surgery.
The only thing I don't like is that its a slap in the face to the genuine disabled folk, who didn't ask to become paraplegics and want to walk again. Its an insult to them.
That said, she can have the operation, as long as she pays for it, and she must pay for her follow up medical treatment, and any other costs relating to it.
If the government recognizes this condition, then she will have to look into whether or not it will be covered.