RE: trying to improve my girls posture with weights!
These workouts may help some, but I would think this is more of a muscle memory thing. Muscles do what you tell them to do, so even if she does the workouts but continues to use bad posture her muscles will recover and conform to how she she holds them with bad posture. She'll have to force her self to use good posture until it becomes habit. Just a guess though. Tell her to concentrate on sitting and walking with her chest out.