Molly Weasley - who had at first been a bit standoffish - was a motherly figure that fussed over Hermione like she was another daughter. If she hadn't spent most of the Summer with the Delacours, Hermione might have been drawn into it. She could easily see just how Potter had been sucked in - not to mention that his godfather (Sirius Black, go figure) was desperately trying to build a relationship with him.