Abby was driving Hannah to the hospital after Hannah fell on the ice. Hannah protested about being taken to the hospital again, but Abby was worried that because of Hannah's CIPA, she may have badly injured herself without knowing it. She was arguing with Hannah about her behavior when she lost control of her car on the ice and crashed. Hannah was hurt, but Abby was badly hurt and unconscious when she was taken to the hospital.
Abby was rushed into surgery while Hannah was taken to the emergency room to treat some lacerations and other minor wounds. Hannah was very worried about her mother, but when Gregory House realized she had CIPA, he realized Hannah would need a full workup. However, Hannah was uncooperative because she wanted to see her mother, and they couldn't sedate her without her mother's consent.
Eventually, Hannah got to see Abby, who regained consciousness between operations.