A few things:
1- Your wife needs to mount the gun properly if she ever intends to walk away without bruises. The butt goes high in the "pocket" formed by raising the right elbow. Her face should meet the stock when she does this, and it will get the buttstock off her biceps.
2- Your wife needs to move her left hand back, closer to the balance point of the shotgun. That way she will not need to lean back, and can actually lean into the shotgun.
3- Your wife is pointing the shotgun straight forward, it should actually be at about a 45 degree angle to her body.
Yes, the stock is too long, and yes the gun is heavy, but using poor form when shooting will hurt more than using good form.