Everything is going to depend on her skins elasticity. Also, there is no telling how fast she will lose weight once she goes primal. I lost 130 lbs with hCG and being Paleo, and my skin is a lost cause. I am also 45 and was obese for more than 20 years.
If she can afford to do gastric bypass, then my advise is go Paleo/Primal, lose the weight, learn to eat correctly, and once her weight has been stable for a year, use the money for lifts and tucks!
Frankly, I would rather be thin and healthy with saggy skin, then fat and sick with tight fat filled skin.