Recommended BP for 83 y/o female

My mother is currently taking Fosinopril 20 mg BID, for HBP.  She saw her Primary MD today, and he still thinks her BP is too high.  In the last 2 weeks her Systolic BP has ranged from 103 to 150.  Her Diastolic BP has been 44 to 55.  Once this week her BP was 180/65.
Today I read an article by Richard N. Fogoros, MD on About.com.  He stated that caution should be taken to avoid reducing the Diastolic Pressure to less than 65-70 in elderly people with isolated systolic hypertension.  Less than optimal lowering of the systolic pressure shoud be accepted in order to avoid reducing the diastolic pressure too far, since the risk of stroke increases.  
My question is do you agree with Dr. Fogoros?  My mother's physician seems only concerned with her Systolic pressure, and keeps telling my mother  she's going to have stroke if her systolic pressure isn't reduce.
Help!

[Momto3]

Hi signy,

I wish I knew more about optimal BPs for people in your mom's situation.  I do know it's very important to keep the systolic measurement under control.  A diastolic reading of 50 or 55 doesn't seem too bad (to me).  Except for the past couple of years, I always had readings around 100-110/50-60, sometimes a bit lower.  But, as long as I was feeling OK, my doctor was not concerned.  How is your mom feeling?  Does she feel dizzy, lightheaded?