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Mary-Kate Olsen will be reunited with twin sister Ashley this weekend when Mary-Kate checks out of rehab after only six weeks.

Although she is cutting her recommend 90-day stay short (she's been there about 45 days), reports indicate the rehab process has been a successful one for the troubled teen, who has gained seven pounds in her time at the center.

But does an early exit from rehab increase her risk of relapse?

"I think that if you leave too soon, you relapse too quickly and it's such a disappointment that it already feeds the original source of the eating disorder and makes them less likely to continue with the recovery," said Stacey Korfist, a program director and therapist at Oceanaire treatment facility.

Oceanaire is an intimate residential eating disorder treatment facility located in Southern California.

"I think six weeks into an inpatient stay is, again, just the beginning," Korfist told us. "I think recovery can take anywhere from two to eight years." She said in order to maintain her health, Mary-Kate must have a successful aftercare program.

"[She'll need] a really well-honed treatment team with ongoing psychotherapy, ongoing nutritional consultations and ongoing weight check ins," Korfist explained.

And while Mary-Kate's reported weight gain is a good sign, Korfist said she has her work cut out for her as a twin. "There's a lot of competition, a lot of comparativeness and I think you have to separate yourself from that identity as the skinny one or as the one with the eating disorder," she noted.

And with both Mary-Kate and Ashley planning to attend New York University in the fall, the girls will also have to face the pitfalls of freshman year.

"Starting college, there's a whole slew of stressors and somebody could easily return back to the thing that helps them which is dieting and they could lose weight and relapse," Korfist concluded.