He felt bad about eating when she couldn't, but he knew it was probably for the better. Especially if they were stuck here for a few days. He wasn't sure if they could make it back to the school by nightfall. And, unlike most males his age, he wasn't very strong. Carrying her would probably be quite tiring for him. Of course, Corona could fly...
No, that wouldn't work. I can barely keep aloft for a few minutes as it is. Carrying someone with your weak body wouldn't work at all. Not to mention you would pass out for a few hours afterwords. Makings the situation even worse. You're stuck here until she can walk.
That answered that question.