There is nothing to worry to travel alone. my mom always travels alone. my parents are coming on 20 nov thru ktm-hongkong-LA-Dallas, and they already bought a ticket. If you could arrange this route, it will be pleasure to assist your mom.
Otherwise, I have a different idea which my fren always use to his mom - providing a wheel chair facility. how it works?--------let the airlines or airhostess know that she had a pain in a ancle or leg and difficculty to walk, then they will take care the rest. Even if she cannot speak english also- no problem, they will do all the services in transit (change 1 plane to other) and drop to the final destination without any extra charges. hassel and risk free A1 service.