As nicholas approached the garden, he might be aware of a slight change, a more alive feeling to it. Perhaps it was the fact that Pamela had had more experience, or maybe just had a tighter relationship with plants, but they reacted to her stronger then her children. While she was certain Bruce knew she was nearby, Pamela was also certain that he didn't know she was just about on the school grounds, which she wanted. 

So she waited for Nicholas to come to her