Slim, the bruising will stop when she has a stock that fits and knows how to use the shotgun.
The standard stock is made for a mythical guy, 5'9" tall, 180 lbs and taking a 33" shirt sleeve. The more an individual shooter deviates from this, the greater the need for a stock that fits.
Trust me on this. The faster she gets to someone fecally cognizant about stock fit and has one fitted, the faster she will get to the point where she's enjoying the heck out of shooting. If she's in pain, not hitting a darn thing, and feels like she's wasting her time, it's not long before she bows out.
Also, a wearable recoil pad, possibly in a shooting coat or vest, will help greatly. I use the PAST pad, and note no diminishing of my testosterone...