I agree with MTS that the first thing you need to fix is the bat dropping flat before she swings. I think many kids go through this. I like the rope idea behind her. Another thought is stand behind her and hold her bat at the correct angle and don't let her drop it. Have her sing into a tee but put a heavy bag in front of it (so she can't follow through and hit you on the follow through). I would do this over and over until she is swinging without dropping the bat head. I wouldn't soft toss until you feel improvement. You will feel it becuase you will be holding the bat head when she starts her swing. If she wants to drop it, you'll push it back up. I also wonder if you give her instant video feedback when you work with her. I would make sure she sees as soon as possible what she's doing and as you work and see improvement (or not) show her.