Feeling tired all the time!?

Girl I know is feeling tired all the time is 18, very athletic, and eats well. She got her blood work done but there were no irregularities. One thing to note was her blood pressure was pretty high even though she doesn't ingest hardly any salt (healthy eater). She becomes exhausted and can hardly pull together enough energy to ever work out now. She gets at least 8 hrs of sleep at night as well. She wants to know if there's anything else the doctors could check for. Any help you guys can offer I will p it onto her. Thanks!