As far as building strength, she should definitely do some weight training, but she shouldn't go all crazy if it has been a long time. For building strength (as opposed to toning, which is what most girls are more interested in, I think), she needs to do lower reps at a higher weight. Most important is going to be her form - slow, steady, controlled reps, pushing forward until failure but not pain.
Classes to build up her endurance would be nice. If she joins a gym, something like kick-boxing or fit-kick would be good for her.
In your post, you're asking someone else to do a lot of work for you in looking up videos and describing something in detail that they couldn't describe accurately anyway. Workout routines totally depend on the person, in my opinion. If your sister wants to develop a workout routine to get her where she wants to be, she should hire a personal trainer and maybe even a dietician. If she doesn't have the cash for a trainer, she should try to find a girlfriend/gym buddy to help her out. Diet is really important, as n3o mentioned - lots of veg, especially dark green leafy veg for the calcium, lots of protein for building up her muscle tone, etc.
