'Legginess' is caused by lack of light. Mst succulents are full sun plants. Haworthia (spiky plant on right) will grow well in indirect sun, but still good light. Your sisters plants are all etiolated, so indirect morning sun is not enough. I can't ID plants because they are not growing as they should, except what I think is Haworthia I mentioned, and perhaps Sansevieria - but could be Aloe? - the green and white striped plant. And there could be coupe of hardy succulents there too - depending on her growing zone/climate, they could be outdoors year-round.

Hopefully dish has drainage hole(s). If planted in such fast draining mix as you mentioned, and temperatures they are in, watering every few weeks could be too seldom.

Some succulents grow longer stems, but still should have leaves growing close together. Leggy plants should be beheaded and re-rooted.