So my sister is just getting into tennis this year. Last year I coached the high school team and she came out to play and ended up doing really well at four singles. Now she is a senior and will most likely be number 1 depending on the new competition. I have been working on the serve with her and she has a pretty good motion going. The best thing is that she is getting tons of slice/kick spin (don't know what to call it) but struggles with getting any pace and depth, usually the ball doesn't make it over the net because of the lack of power. I know that she isn't snapping the wrist through the shot but I'm not exactly sure how to get her to do it? Any suggestions?