^Confusion nowadays places 3 damage counters, not 30 damage, on the confused pokemon. That makes a difference as it isn't affected by weakness or resistance nowadays (b/c it's counters). It used to be 20 damage that had weakness and resistance apply for the damage. (not trying to be completely picky but it could confuse someone...)
Just say that the rulebook agrees with you. Show it to her if she still doubts the retreating thing.