[Healing someone normally isn't too power-consuming, because it simply requires fixing something that is already there. But in this situation, there is nothing to work off of. To get Akito to return to normal, she would have to 'trade places' with him in terms of energy. And though she would like to help him as much as possible, it wouldn't be good for her to just fall over. Especially since she still had to report to Lelouch and help at least some of the others. Therefore, when she places her hand again on Akito's forehead, she reminds herself not to get too carried away. She should give him just enough power to wake up and be able to eat and talk.