"But I remember when trees were everywhere"
Norma remembers her first time seeing the valley. It was like nothing she'd ever seen before. And when she first met Once-ler, it was much the same. Wasn't hard to see how they were completely and utterly smitten with each other.
Once-ler would take Norma through the valley, introducing her to all the animals who he'd come to love as much as she loved the majestic beauty of the truffula trees.
She remembers watching as the valley was torn away, tree by tree, tuft by tuft. She remembers begging Once-ler to stop, on her knees, crying at the dark desolate destruction. She remembers watching him change from the man she loved to someone she hardly recognized.
She remembers the last tree falling. By that time, she was packing her bags to move into town. It wasn't safe for her to be out there at that point, not with her baby on the way.
As she moves into her new home which looks nearly exactly like the next, she remembers the alley and for a while, she keeps pictures to remind her of the way things used to be. But then it becomes too painful and she has put them away.
Years later as she stands firm next to her grandson, she remembers everything so clearly and is willing to fight for what was lost.