You shouldn't lie about your health.
Linda woke up late on Monday morning.
Linda wants to take the day off of work.
Linda calls her office and tells her boss that, while she is not physically sick, she really needs a vacation day.
Linda calls into her office and tells her boss that she is feeling sick and won't make it to work that day.
Linda feels as though she has done the responsible, adult thing in the situation and her boss has no reason to doubt her sincerity.
Linda feels dishonest and her boss questions whether she is telling the truth, creating an awkward dynamic between them.