I've got several bent sharply at 90°, it broke the skin on the main stalk, healed, and now the "top" of my large sativa is growing upward again, it is tied off to my cage to keep it supported so the high winds dont rip a quarter pound branch off. So yes, you can bend at 90°, I pinch the stalk in my fingers tight, about 1.5' down from the top, the bend it down slow to avoid snapping it off.
You plant is growing up, not north, by bend it in a northern direction, I literally mean bend the top to point north so the side facing the sun will follow the east to west pattern of the sun and make the entire side of it to become tops on every branch.
You can also "rainbow" bend it, same effect with less initial stress for both you and the plant, snapping branches and stalks at 90° isn't comforting in the beginning years of a grow career, it still chokes me up at 10 years sometimes. Even if you do break the top foot or so off the plant, she will survive and bush out instead of getting taller, so you could just cut a foot off the top and she'll work on becoming a fat girl, my favorite!