With the luxury of having the room all to herself, Hermione drew a proper summoning circle out in chalk with runes, and activated it with a sacrifice of a mouse (thanks to Crookshank’s hunting) and an invocation, as she waved her wand around. When done properly with all the ritual trappings, calling her friends took less magical energy from her and was less tiring, though honestly it was never terribly difficult for her thanks to repeated practice. Whatever wards Hogwarts had against Apparition, she’d determined that they never seemed to interfere with her friends’ comings and goings as she’d feared they might, thankfully. In fact, it seemed if anything slightly easier than it had at home.