Talk to the coaches. I presume you mean that she conceivably could be on a senior team? How old is your cp, from your mentioning youth/Jr, I'm guessing quite young - 9? If you are talking about a senior team, what would be the age spread - would she be the only younger girl or would it be a senior team made up of a range of different ages? I ask because if, for example, your cp is 9 and the other girls would all be, for example, 12 and older , or 14 and older - personal opinion -don't do it. This last season my daughter was on a senior team with ages from 9-16 (small gym, harder to level out ages and skills.) It was no problem because the ages were fairly evenly spread out, no one was at one end of the spectrum by themselves and being from a smaller gym, most of the cps knew each other anyway . But I would say that is probably the exception to the rule. Worst case, she would be the only younger girl, she might get lonely, some of the older girls might resent her, she might hear some conversations not appropriate for her age. (I did say worst case, remember.) In other instances, the older girls take care of the younger cps and are very protective of them. If your cp is as young as I have presumed, she has plenty of time to move up. Most that age would enjoy being with their peers more than moving up a level. The make-up of the rest of the team is probably the most important consideration, which again takes you back to the coaches. Don't know if that helped, but good luck. (Did I mention talk to the coaches?;))
Just as an additional note: there have been many discussions on various threads about little cps on senior teams - most people don't like seeing it.