Legion of Super-Heroes: Millennium #1

Rose Forrest visits Supergirl, President of the United States in this time and place, to warn her that Thorn (her violent personality who has been kept at bay for a long time with medication) will be loose once the medication she is no longer taking has worn off, and since it is no longer being manufactured, she will be unable to control her darker side. Rose is worried that Thorn will be angry and kill people. Rose also worries that she does not recall what happens while the Thorn personality is in control of her body, and it might account for why she doesn't appear to age.