Im at the Ballas boss fight and I cant control the lotus beam. I know I have to hit the mirrors but I cant control the beam the lotus fires at me because it just goes spastic and flails around everywhere. I tried a control and a mouse to no avail.

Don't stand too close to her. The maximum angle for the redirect isn't large, so being farther away and facing in the general direction of the kuva mirrors helps.

The only clue I can't give without spoiling the fight is Bait.

Stand with Lotus between you and a mirror in more or less a straight line.