...."hockey stop" is not necessarily a method of stopping that I recommend for any beginner and in fact, I feel like hockey stop can imply stopping while out of control.
^^This.
The best way to teach beginners to stop is to have them turn all the way across the slope with the intention to make a U-turn. The skis will refuse to go uphill and will coast to a stop facing the trees.
On the beginner slope, work with her on making successful turn-stops in both directions. Turn and stop left. Turn and stop right. Repeat, repeat, repeat. She can be in a wedge while learning this. The wedge will be important for her since she's fearful - it will give her confidence that she has some measure of speed control, at least as long as she's skiing on beginner terrain.
Once she can turn-stop on beginner terrain, work on shortening the across-the-slope distance these turn-stops require. Once she can make turn-stops without taking up much of the trail's width, have her link these turns, attempting to almost coast to a stop with each turn. Her turn-stops will morph into completed turns.
On beginner terrain still, she will be making short radius turns in no time, in a wedge, going stupid-slow down the hill, and she will be able to stop on a dime at any point with a turn instead of a braking wedge. She needs to learn that completing her turns slows her down and stop her if she chooses. This is a major realization all new skiers need.
After she's good with linked short turns (in a wedge), have her work on moving the inside ski over to match the outside ski half-way through each turn. This may take some time. Stay on beginner terrain for this. Then work with her to move that new inside ski (it's the downhill ski at this point) over to match the new outside ski before the skis point down the fall line. This is a very big step, and takes time and persistence to learn. It's learned best on beginner terrain.
Once she can reliably slide that inside ski over to match the outside ski - above the fall line - she will be ready to go up the hill onto green terrain where that wedge won't do much for speed control. Stay off blue terrain.
On green trails, go back to having her doing turn-stops in both directions. She will probably take up a lot of real estate with these first turn-stops and be concerned about the speed she gathered before stopping. This is normal. Have her shorten the distance she uses to coast to a stop. Next is linked turns.... slowly bring her through the same progression you used down on the beginner terrain until she's aware that the shorter these completed turns are, the less speed she gains. She needs to know this to have the confidence to continue skiing and building her skills.
Teaching a beginner or novice to do hockey-stops is difficult in the first place (the reasons are listed upthread). If taught to her early, the braking hockey stop technique will get embedded in all her turns. Braking in each turn will replace using turn shape for speed control. And the conceptual approach of braking will inhibit her ability to advance as a skier. Teach hockey stops to her later, and emphasize they are for emergency use only.
Some people learn faster than others and don't require such a slow progression. Do not rush her. Everyone learns at their own rate.