Another thing, we were told that the abnormality is hereditary. Really?

No. The doctor could be wrong on this one. Some arthritis could be hereditary. Not that it is 100% certain that this particular one is hereditary.

This hereditary stuff can be unsettling! There was a time when I visited the hospital for a checkup after an accident. The doctor assured me that my concerns were baseless. However they suspected a hereditary problem with my eyesight. I consulted my family about it. No member of my family, to the best of our knowledge, ever suffered from such problem. I dismissed the diagnosis and enjoyed peace of mind ever since.

According to the doctors, surgery is 50/50. Meaning that while what is broken can be fixed, new problems can be created. She may not be able to walk after the surgery.

Please don't go for surgery. Let her think of an alternative means of generating income that will not worsen the problem. I do sincerely pray that the problem will not degenerate.