What is break?I've always read and been told no more than 45 deg, but less is okay. DD is typically at 45deg. The local HS Varsity pitcher (who is very very good) is much more like the Monica Abbott style. As long your DD can establish a good strong break then I think it comes down to what works best for her. If she needs help not opening as much maybe try making her think about landing less than 45 on the toes (ala Abbott). She'd be forced to keep her hips more square to achieve that.
I'm a huge proponent of the "balance beam" as a tool for FSR and balance. If the break is weak, pitcher is striding off center (by a lot), or not staying square (monkey butt)...then they will step off. It's an instant feedback/consequence tool. We use a 2x8 for DD. Once the issue resolves we put it away for a bit, but is something we revisit multiple times throughout the year.