After Nil, Lucy, Mindle, and Asilean left the tent, only Toz and Scrael remained. Toz looked at Scrael after he sent the others away, but she was too absorbed in the grimoire to care much about her surroundings.
Thankfully, the tent had privacy and security enchantments. They weren't completely impenetrable, but it was enough for Toz and Scrael to concentrate on their training without worrying about any interruptions. Though even if they supposedly didn't have to worry about anyone intruding on their tent without their permission, they still wouldn't completely let down their guard.
Scrael, especially, didn't let down her guard. She had spent her whole life facing constant threats to her life, so she couldn't relax enough to be caught by surprise even if she wanted to. However, her instincts didn't quite reach Toz, so she wouldn't be able to warn him if he was attacked first.