She is having all of her organs repositioned and propped up. The doctors instructions offer 3 types of pain relievers and explain many types of complications. She is claiming that she will be able to take care of herself and that she doesn't want help from either someone in her family or a professional. If you have had experience yourself or know someone who has, please let me know how long it took to feel good and when the patient was able to solely take care of themselves.
I agree with vstefans, just make plans and be there whether she thinks she will need help or not.
Fortunately, you can enlist the aid of the social worker and doctor at the hospital. They can't release her unless she has someone to take care of her or she can take care of herself. Be sure to have conversations with them about your mom's resistance to care and spell out that she won't have support if she returns home alone. There's a good chance they'll give her a stint in post-op rehab anyway, but there, too, make sure she's truly able to care for herself when she leaves. If she fakes them out and goes home alone without care, she could start an downward spiral of repeat hospitalizations. At her age, she's in the danger zone for that.