I have emailed my SIL who is an internist for Kaiser in LA to see who she recommends. The biggest question I would have for any doctor is it safer to have the surgery in LA then travel back to NY, or is it safe to delay. Part of the answer to that question is if there is circulatory or nerve problems that would worsen if surgery was delayed. The other is the risk of developing a DVT (clotting in the veins of the legs). Generally this is greater right after a break and right after surgery, so either way your mother would need recommendations about possible blood thinners and length of time she should wait before getting on an airplane.
I am so sorry this has cut your mother's vacation short. I am a nurse practitioner in a resort community ER and I see this a lot. I wish her nothing but the best. The airlines are generally great about making sure your mother will get more leg room so she can prop her leg better during the flight back. An MD, NP or PA can write a note for the airlines. And, of course, a wheelchair from the door of the terminal onto the airplane can be arranged by a phone call to the airlines 800 number.