Sudden extreme spike in blood pressue

I hope somebody can help me.  My mother has had healthy low blood pressure all of her life and she is 60 years old right now.  Her blood pressure is typically about 104/60 or less.  She has never had any health issues or heart problems, and heart problems don't run in the family.  Within one month or less her BP has shot up to as high as 159/80!  When I have tried to get her to take deep breaths, relax as much as possible, and test on the machine at home the absolute lowest it got was 140-145 systolic, which is still much higher than ever been.  She went in for a routine physical for new health insurance and of course they were alarmed.  They did a EKG and found palpitations so they will do a 24 hr monitor in a week to access damage/problems.  She admitted that she had been having what she thought felt like palpitations for about a month, but attributed them to temporary anxiety related.  This past month she had been under some strain helping her own mother move into a smaller home and it's been tiring/stressful.  She has been done with that about a week and has not been under any great stress.  My question is, could just the stress of helping someone move make your blood pressure shoot up that many points after a lifetime of low BP?  Could it still be temporary?  I know there could be unlimited causes but what would be the most common cause of heart palpitations and/or a spike that high?  I am so worried about her.