Ok.
First of all, have you done the sidequest for the sakitron ?, if you have then Sakitron is able to deal more damage, if not then you have to play this very carefully
Secondly, on how to win: Along the battle, Amanda will monologue a few lines before starting your turn and in that line, there are specific words that correspond with your attack, example: Amanda: "How many time I must hammer you before you understand" -> use saki hammer that turn. There are several others but this one is what I remember
Third, When she/it prepare for laser u should use your fourth move sak