I'd check and see if the skin itself tore or she has some retained skin. If it's a retained shed, you shouldn't see white/pink down the tear line. If she actually tore her neck skin just eating by herself (not being forced) then I'd be highly suspicious of hypovitaminosis C (lack of vitamin C). Snakes get their vitamin C from the rodent's diet. It's possible if the snake is eating mice that didn't eat for several hours prior to being euthanized or fed to the snake, that they have empty intestinal tracts and therefore don't provide any vitamin C to the snake. The classic case is when people buy live rodents from somewhere and they've been sitting there a few hours not eating, you buy them and take them home, they sit another couple hours, so that by the time they are fed, they've emptied their intestinal tract.
In any case, if she really tore her skin, you need to protect the area from getting infected while it heals. Honestly, it would be best to see a herp vet to ascertain severity of the wound and if it needs stitched. Keep her in a dust free enclosure, use paper for bedding, DON'T use peroxide on the wound, it's detrimental to deep tissues. A little triple antibiotic ointment or a very weak betadine solution may be used. It's also best to not feed her for a bit or if she's very young to just feed her very narrow meals that won't stretch out her skin. Adding a bit of vitamin C to the meals may be necessary if it's truely the result of vitamin deficiency.
Best recommendation is talk to a good reptile vet.