The thing is, when you go cold turkey on certain kinds of foods or drinks, it can early on translate to all sorts of side effects.  I remember when I quit soda cold turkey. Just one day decided I needed to stop, and never touched soda for over 5-6 years (once in a blue moon I may have a specialty soda during a special occasion but I normally can't finish, it's still too sweet). Headaches from hell, dizziness, legit feelings of tired/weak. Lasted for a while but then it was all better from then on. You get so used to feeling bad, it's amazing to suddenly feel good. It's probably tied to sugar/caffeine withdrawal. Not to say the low blood pressure isn't an issue, or she may not be doing something right...just that when you quit some things food/drink wise the side effects can be pretty bad for a bit.