I've seen a few talented girls playing up a year until about U10 or U11, when they were placed back in their appropriate age group. Depends on the club and level of competition. Based on your location, yes OP would be one of the better options to look at for next season. Club Ohio and Barcelona United would also be fine for the next few years at this age level. In Dayton, you're looking at BSA Celtics and FC United. A little further south, there's Warren County (WCSA) and Cincinnati Elite. If you're willing to go all the way to Cincy (which I wouldn't recommend until at least U10), there's a plethora of options including Cincinnati United (CUP), Kings Hammer (KHA), Ohio Elite (OE), and Total Futbol Academy (TFA). Consider the additional cost of moving to one of these clubs. Some are twice as much as others (not including travel expenses), and none of them are what I'd call
cheap.
It's worth noting that beginning at U13 (formerly U14), girls can compete in the Elite Clubs National League (ECNL), widely-considered the most competitive format out there. Clubs in the region with teams in the ECNL include OP, Ohio Elite, and recently-joined Kings Hammer.
Important thing at this stage is to avoid overwhelming. Let them connect with the sport first and develop a deep love for the game. At any decent club, they're going to get all the training they need to be successful in the early years. You can always transition to a more competitive club later depending on how she's developing. As for a personal trainer, you'll get varying opinions on the need for that. My daughters went through the system just fine without one, all the way to playing D1 in college. They attended a few "group" sessions with a trainer and went to couple camps in the offseason over the years, but nothing too intense. I couldn't honestly tell you if any of that made much difference, other than giving them additional touches between seasons (and taking more money out of my pocket!).
Also keep in mind that as they grow, strengths and weaknesses will change, as will the competition around her. Others will eventually catch up and may even surpass in some respects, especially as she moves into more competitive play. Don't let that discourage you when it happens. Those that stick with it will find new strengths, hone existing ones, and will learn to play different positions. They may eventually settle in one that is very different from where they started.
Fun times ahead! The best part is all the people you'll meet along the way! I really miss that. Wish her luck on her journey!