I think for the VERY unconditioned, it is good. But if you go consistently, you will "outgrow" it VERY quickly. Curves is quick, not intimidating, uncomplicated, simple. There is no thought process involved, no guessing on what to do. This is nice for the newbies who are overweigt and intimidated by a traditional gym. Many of these women are older, never worked out, and are overweight. No matter WHAT they do, they will lose weight once they become active! lol
I had a girlfriend, who is in her early 30s, who wanted to lose about 10lbs and "get toned" (blech). She started going to Curves, went for 2 weeks. Dropped that and joined Gold's. She quickly realized that she was not going to reach her goals THERE.
But if she likes it, then good! She might outgrow it, she might not. Just let her know that if she ever wants a change of pace and come workout with you, then she can.