Louuuuuu
Uuuusually Yuuuuuo are right; but not this time.
If you are want an 18U lights out pitcher the last thing you should to do is even mention the strike zone. Your dd needs to throw with effort, she needs to develop getting her arm in the slot, accelerating to the end and feel the ball snap off of her finger tips. If her hand is small use a small ball (even consider using a baseball) so that she doesn't compensate by pushing the ball like a shot-putter.
Sure start at 10', move her back to 20' then 30' then 40' then more. Most girls are very careful and need to get 'big'. When a kid is throwing a baseball (or a softball) 80' she has to extend and leap and really whip her arm followed by a strong wrist snap through the entire circle. You can use a 300' tape and lay it out on the ground and just have her throw balls down the line. This forces her to get 'big' and stay 'big' but she will have to stay inline and then make maximum effort. (you can call out the distance on each pitch)
If you bring up throwing a strike she will get small; she'll lean forward, shorten her arm circle, and try to be careful. (BTW: Never say 'just throw strikes; ever) She needs to throw with abandon and if it goes over your head great.....move her back. Right or left is caused by poor mechanics and can be corrected. You want her constantly pushing to throw harder and then harder (Read further and further again).
She will be terrible and will walk twice as many as she strikes out. She will hit a ton of kids. If you try to make pitching about putting the ball through a 17"x30" box she won't make it out of 12U. She is asking her body to perform a very precise set of motions, in order, at a very high rate of speed....and then she grows and gets stronger and she has to relearn them again at a higher rate of speed .... repeat.
She won't get it as a 9 year old, but by 18 maybe she'll take the team to States.
Get your dd some lessons even if it is part of a big class or give the local high school pitcher $20/an hour to work with her. Unless you have several dd's, you can't waste one while you learn. Get good mechanics right out of the box and then throw 'BIG' (a lot). Get a bucket of used balls or two, don't pick any up you can't catch, let 'em go, this is about throwing and learning to pitch not about you catching. (Oh and get a bucket: you'll be catching 50,000 pitches a year for 12 years..... and your knees can't take it) (Oh, for gods sake; don't criticize every pitch, find something nice to say or just keep your mouth shut, she doesn't need to hear you constantly yammering)
Good Luck