My aunt took her high blood pressure twice?

maybe nothing, but possibly her blood pressure could drop low. She should probably drink some extra water to be on the safe side. If she gets really dizzy or lightheaded, it probably means her blood pressure is dropping too low, and she should probably get to the emergency room. Have someone else drive her there so she doesn't pass out. If she feels ok, she will probably be fine.

If she keeps the insert from the drug store that comes with her medicine, it will direct her what to do if an overdose is taken. If that is missing, she should call the local emergency room staff and ask them if she should come in. She should take it seriously.