My fiance has started to have a resting heart rate of around 100 when she was not previously experiencing any sort of elevated heart rate. She came home today and told me that while at work she climbed a flight of stairs and her heart rate was around 160.

She is only 23 and has no history of any cardiac illness and I'm starting to get really worried about her, but she won't even make a doctor's appointment as she feels fine. This isn't normal is it?