The Benelli's tend to have a long pull. The adjustable stock will do better for her small frame.
The M4 is a great gun. Since you have a Benelli semi-auto, have you considered a Nova Tactical pump? It doesn't care what you hang on it, and it will eat any 2 3/4, 3, or 3 1/2 regular or magnum load. Chromed receiver and barrel. Smooth action (smoother than the M3 in pump-mode). Magazine override so you can eject and manually load with rounds in the tube. Lights and sights. Optional recoil damper for mag loads. Sling-ready. Fully decked out for a good bit less than the M4.
The M4 is a great gun. Since you have a Benelli semi-auto, have you considered a Nova Tactical pump? It doesn't care what you hang on it, and it will eat any 2 3/4, 3, or 3 1/2 regular or magnum load. Chromed receiver and barrel. Smooth action (smoother than the M3 in pump-mode). Magazine override so you can eject and manually load with rounds in the tube. Lights and sights. Optional recoil damper for mag loads. Sling-ready. Fully decked out for a good bit less than the M4.