fastpitch hitting

Question
How do I cure my daughter from hitting weak pop ups and hitting the ball off the end of the bat?  She is 12 years old and 5' 6" and she weighs 110 pounds. At the start of this season I bought her a new bat -- Easton Typhoon 33" and 23 ounces.
Her old bat was 32" and 23 ounces.

She has played fastpitch for 5 years, and she has been a pretty good hitter to this point. But ever since the new bat was purchased her hitting has been awful.  I have worked with her on a batting tee including having her swing with the lead arm thinking she was "cutting across the ball" but that did not help.  I have also worked with her to keep from dropping her hands at the start of her swing but that has not helped.  

Is the new bat too light? Too long?  Is it simply a matter her swing has changed for the worse?

Answer
Hi Jeff, may i ask why the change of bat? When there is a swing change, usually it's not the bat that causes it. Ask first your daughter if she's unhappy with the change of bat, if she's ok with it maybe you can ask if she notices the changes on her swing. Listen to her answer maybe you'll find the solution there. If she's ok with the new bat, take a video of her swinging against a pitcher and view it a slower speed.

Maybe the pop ups are happening because she has a hard time adjusting to various pitches. A change up may cause this, teach her to wait and a bit then swing her usual swing. Change the way she approaches the ball,have that little delay.

Hope this helped.