From what I can tell from videos, it's "supposed" to help correct arm circle??
Non sugar coated opinion: Parents who are serious about their daughter's development as a pitcher should FIRST seek out a qualified pitching instructor. I know that's sometimes "easier said than done", but learning pitching is not a frivolous task that can be learned in a short period of time. IMO, it is the most difficult position to master, with hitting skills a very close second.
There are plenty of existing training aids for pitching - many are inexpensive (but effective) home made devices. But before using ANY training aid, you should consult your pitching coach and have a conversation about the pros and cons of the device. Otherwise, you could be working against what your instructor is trying to achieve. There are plenty of existing drills for just about any mechanical flaw that exists in a pitcher's mechanics. Many flaws can be improved or eliminated simply through proper practice technique.
I'm not saying that all newly invented training aids are worthless. But you should scrutinize the value through a cost versus improvement consult with a qualified instructor. Otherwise, you'll wind up with a closet full of useless expensive "junk", where the money would have been better spent on training with proven devices.
Good luck - happy pitching!!