The volley of jinxes and hexes that followed ranged from moderately annoying to devastatingly painful and the room absolutely reeked with spent magic. Blair wildly deflected Confringo from Hermione set Hela's desk alight and, after magically shoving the thing in Briar's direction, Hermione was forced to recalculate. Her magic was starting to behave erratically - too much brought forward too soon after being gone for too long. Add in the use of a new and not totally won wand also contributed to how quickly it was draining her. She knew she couldn't rely on her spells doing what she needed them to for much longer.