I think this girl either is pregnant or could actually be ill from the medication she says she is on. All people react differently and some medications are very likely to make you ill if taken on an empty stomach and others make you ill if taken on a full stomach. I wouldn't worry about it because I'm sure she's not contagious because if she thought she had the flu or something, I'm sure she wouldn't continue to come into work.
What lies behind us and what lies before us are small in comparison to what lies within us.