Many hunting and arrow "experts" recommend 25-39 ft lbs for thin skinned game (deer, antelope, etc). A wide range probably due to the fact that even within the same species (like deer) does, bucks, and yearlings are very diifferent.

Here is a KE calculator:

Bowhunting Info Kinetic Energy Calculator

Great post by davidmil, I also prefer sharp coc broadheads(just my preference) and the most weight she can comfortably draw.