Rehab and Depression Help Centers Do They Work?

theres this center for adolescents that my sister just went to it’s for depressed girls that have cut before or have used drugs.. it was really sad to say goodbye, we get to visit her but the minimum time she stays there is 30 days..there were some other girls there so i hope she makes friends..does anyone know if these places really work? im scared but i just want her to get better and change.. thanks a lot <3