Honestly, satsuki is going about this the wrong way. Instead of flat out telling them she should just purposely hang out with them like an overbearing friend or something.
My guess is hair dryer + swim club = electrocution. It was an obvious potential cause and since Satsuki didn't immediately point it out so that it could be a red herring like the oil paintings, it's probably the true cause.
Beside searching how she die, i want to point out that it's the second time Komachi is suposs to die. I think Komachi was bound to die and now, whatever force is behind that is trying to make it happen.