>>149671973
Been like a decade, but IIRC Lisa did that thing she sometimes does where she has a mental break once she realizes she's only "smart" in Springfield and gets blown out of the water by actually gifted people.
When the girl she was taken down a peg by ended up in a life threatening situation, Lisa left her to fend for herself. She later caved in to the guilt, confessed everything, and the girl was rescued.