MBG, I think you should google it. There are tons of websites about soundproofing, some very technical. I was looking into it because I live in a small apartment and live next to and below very noisy neighbors. The best thing to do is get a professional to look at your space and make recommendations. It doesn't always necessitate ripping up floorboards, but from what I recall, wood is a big conductor of sound. Sometimes sound will still travel along beams even when soundproofing is applied to walls. And there needs to be air space in between and sound baffling material used. You may want to add specially made ceiling tiles to her room and make sure you have carpet in yours. Google around and you will find lots of info on it.
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