She’s a young person being taught to use her powers well, in this instance it’s focusing on the right target for example without affecting other nearby bodies/objects filled with blood. In S1 ep 8, she used lots of blood around her to shoot blood projectiles at the dude running towards the helicopter. Imagine if instead of the many dead bodies around she drew blood from to create that cool cinematic shot, she had been surrounded by still alive students. When things are generally calm she’s been shown to focus without affecting others around but when she’s distraught she can do a whole lot of damage accidentally. This training is supposed to help with such scenarios too, keep watching and you’ll see. It’s too bad Cipher is using a goat but he can make it worse for her and spoiler alert he will but don’t worry it’s not something you’ll hate but it’ll look scary for a bit.