Why was she mixing it in the first place...normally you just sprinkle the SHOCK granules all over the pool surface.
My pool has been open since May 21st and that was the only day I needed to use SHOCK. Since then I maintain it regularly with 3 fast tabs in filter basket every other day.
One oz. algeacide weekly and one oz clarifier weekly. Its crystal clear even after 10 kids are in there.
I run filter 8 hrs per day.
I know of some people who simply pour bleach in their pools and get similar results and save a bundle.
In lieu of a clarifier additive, one method of flocking a sand filter is to disolve granulated Shock in a plastic pail of water and pour into the skimmer and filter the water for 48 hrs. What it does is tighten the space between sand particles so smaller particles can't escape. As that happens, the filter's efficiency increases as more smaller particles are trapped. Sort of a cumulative effect.
One better method is simply to not backwash the filter so much - maybe once per week or when the pressure is above 20-25 psi.
Either way, chlorine should NEVER be disolved in a house or an enclosed environment.