I actually had her try out the Mossberg 510 youth model in .410 bore but she's already outgrown it. That's good because the 20 gauge will throw significantly more shot and 20 gauge slugs are adequate for deer.
Both the stock and forearm are synthetic. The stock is currently setup with a 12" length of pull but it included a spacer to increase it to 13". If she needs a longer LOP it will accept adult-sized stocks. The stock has a good, thick recoil pad on it.
The 22" barrel is threaded for choke tubes. It came with the modified tube in place. Using the included wrench, I swapped that out for improved cylinder. It also comes with a full choke tube. The barrel is topped with a white bead up front and a brass middle bead.
At 5.25 lbs. unloaded it won't be hard for her to carry afield. Heck, that weighs less than her school bag on most days. The stock has a place to attach a sling swivel but the gun didn't come with a stud for the front. So, I found one on eBay and it should hopefully be here by the end of the week. It will thread into an existing hole on the barrel mounting screw. I also ordered an inexpensive sling with swivels and an Outers cleaning kit.
The magazine came plugged so that the only way to load it was singly through the ejection port. The manual states that once your new shooter learns gun safety you can shorten the plug (a dowel) to 9", to allow up to two shells in the magazine. I did so, since my kid is not new to shooting. (Frankly, if they aren't safe to handle a manually operated gun with 3 shells in it, they aren't safe to handle a single shot.)
The unplugged magazine capacity is six 2-3/4" shells. I have some Federal 20 gauge #3 buckshot with which I'll pattern it. It would make a nice home defense shotgun.
Aside from hunting, this will be a good shotgun to introduce my daughter to trap and sporting clays.
Of note, Mossberg has a similar gun in their economy-oriented Maverick line. However, spending more money on the 500 was worth it to us because the Maverick uses a right-handed cross-bolt safety instead of the Mossberg's ambidextrous tang safety. I'm a lefty and my kid is left-eye dominant, and hence shoots portside.
I'll post a follow up after we get the chance to shoot it.