He was right about the vampires here. Most were trying to do what they could to help the humans or others than weren't able to safely venture out on their own. Lissa and the other Moroi had that problem, but she still wished to help where she could which was why volunteering for the medical staff wasn't a hard decision for her. She knew that the doctors liked to do some of the caring on their own, but she healed those she could even if she knew in the back of her mind that the spirit could come back to haunt her. Not using the ability wasn't an option.
Lissa smiled brightly when he took her up on her offer to run. She wasn't sure if she would beat him or not since even in this body he had more experience and was used to how to use the speed he was given, but she didn't care. She took off at a run quickly and didn't look back because she knew he would be following her without a moment's hesitation. The magic would be reversed and she would be back in her own body soon, but for now she was taking advantage of the switch as much as she could. Wind in her hair, she let out a light laugh as they ran back to the house. Being one of the Cullens was hardly the worst switch she cold have imagined.