In regards to injuries from foot first slides.
If you were to watch 100 girls slide in a game I would estimate that more than 90 of them would be foot first slides. So it makes sense that there would be more injuries from sliding foot first because it is done so much more frequently that a head first slide.
Now if you were to watch 100 girls slide head first, and then watch another 100 foot first slides. I would certainly expect there to be more injuries from sliding head first.
I don't really see why, unless they're sliding headfirst wrong. Almost every headfirst slide injury I've seen from pro ballplayers is because they're just not doing it correctly.
And even if there is a slightly higher risk, well, they're playing a sport. There is always a risk of injury. We want to mitigate those risks as best we can, but I'm not going to stop my players from performing a perfectly reasonable, viable, and sometimes necessary act because there's like a .01% higher chance they'll get hurt.