I use a 20 gauge 1100 when I take my daughter in laws out for a round of skeet. They love it but it is usually a learning experience since we don't go very often. They say their arms feel like rubber after a round. These are not lightweight guns. I cannot imagine a 9 year old, unless she works on a farm, being able to comfortably use an 1100 to learn on.
When I shoot the gun is up for only a few seconds but when someone is just learning it seems to me they have to hold the gun up a lot more from inexperience and all the teaching of how to place and hold the gun in the beginning.
A $300 aluminum? receiver gun is not probably gonna hold up for a million rounds but after its duty as a teaching youth size gun is up it can be sold for $200 or traded in for a break open gun which will kick a lot harder but the girls will be older and stronger.