Lots of good things mentioned here to consider. Age does make a big difference as has been said. At older ages it also affects recruiting, coaches are looking at years based on graduation years and if your kid is playing up they could get missed by the coaches looking for her year and seen by coaches who don't have an opening her year. She can work around this is she is very proactive about inviting coaches to games, but it's one more factor to consider.
Many clubs will discourage playing up because it is done for the player's benefit not the club's benefit. Having a star player play up will generally hurt the younger team more than it helps the older team so clubs don't like that. Naysayers are going to say I am BSing so here is a link to an actual local club play up policy which states that quiet part out loud.
https://www.sycva.com/page/show/477125-play-up-policy The important thing as a parent is to find the best fit for your child where they are happy and learning wherever that is.