i can understand your concern, it would have been better if you had mentioned the recorded blood pressure and also if she was facing any symptoms.
see, many people have a systolic blood pressure in the range of 100-120 and the diastolic blood pressure in the range of 70-80, it cannot be considered low, its normal for them, it depends on their nutrition, body type, weight etc,
so don't be worried much. ask her to drink lots of water and other fluids and have a good healthy balanced diet.
consult a physician for further evaluation. best regards,
Dr. Anil kumar Jain
Hi there I understand your concern...there are many causes hypotension includes bradycardia,para thyroid disorders,low blood sugar, Addison's disease,pregnancy, anemia,certain drugs like diuretics,alpha blockers,beta blockers etc...I would suggest you to consult nearest physician clinical examination and evaluation they will do the needful.