double movement in Scrabble
From the official rules:


  All tiles played in any one turn must be placed in one row only across, or one column only down the board.


As you know, it is perfectly fine to score for multiple different words you made on your turn, but only if you made them from tiles played that turn. Since any tiles played on that turn must be in a single row or column, you cannot play two letters in one column and start a word, and then finish it by playing another letter in a different column. If I'm understanding your example properly, then you are correct in that she made an illegal move. :D