Pitching drills for inside the house.

[fastpitch91]

Way back in the olden times when DD was 9 I made her a target zone with a gymnastics pad and some walls to catch any errant pitches - down in the basement. Used real balls, no socks for her. Broke every light in the entire basement! Regardless of location. I swear she could throw a pitch around a corner and break a light in an adjoining room. Replaced the lights and built chicken wire protectors for all the fluorescent tube fixtures. Nothing like real balls to learn with !! Must have been a rising-double corkscrew curve ball !!

 

[Veryzer]

<soapbox>
The traditional wrist snap is a fallacy, and it's impossible to time if you're trying to go full speed and just "think" about when to snap without a physical cue. Watch slow mo of good pitchers, you'll see the release motion does not resemble the traditional wrist snap.
Sounds like you've got a hello elbow teacher. Not to be rude, but all successful pitchers learn to pitch in spite of the wrist snap instruction, not as a result of it.
Sounds like you're underway with the research. Here's a playlist I put together to help parents with I/R pitching.
Search this site for I/R in the classroom if you want to really get into the weeds.
</soapbox>

That playlist is an excellent resource. Thanks!