To me it seems the dogs responded like any normal predator.
Her sking down the hill triggered the chase instinct so many animals have.
Whats the worst thing you can do if confronted by a mountain lion? RUN, they will chase you.
Alot of animals will give chase and attack if you run away ( ski? ).
Had she ever had them in that situation before? They may be the most docile animals normally.
When I lived in Montana I
had a Rott / German shepard mix who was the greatest dog ever.
We found out when we took the kids sledding that once they got some speed on a hill he would run along and grab a mouthfull of my kids coat (and arm) and start biting / pulling viciously. My son ended up with fairly serious bite marks. If you notice I said I "had" such a dog. (.357
The pursuit triggered something in him. I loved that dog but he was untrustworthy and I sent him to have a talk with mr. Ruger.