Fatigue is real. The activity is supposed to be fun, not punishment.
She might like to start with a round of skeet or 5 stand, just to limit the gun carrying and recoil. Much less strenuous than walking a course carrying a gun and cartridges.
I have found that it takes a while to build up the strength and endurance to shoot all afternoon.
3/4oz loads will really help.
If her shoulder pocket is getting warm, or sore, she's not really ready for greater volume. It takes a while to strengthen/toughen up that area.
No need to make yourself sore right away if the activity could potentially go on for years Ease into it. Her muscles will adapt.
