Extreme High Blood Pressure

My mother has been experiencing extreme high blood pressure over the past year.   A couple months ago she was in the hospital where they did an renal angiogram that came back good.  They also did many test that looked at adrenal glands, kidney disorders and endo disorders.  All came back normal.  Her blood pressure was in the 200s over 100s.  A couple weeks ago she went back to the hospital for a week when her blood pressure 200s over 100s brought fluid on her lungs.  She had a heart cath where all looked good.  No blockage it did show that her heart is looking leathery from the high blood pressure but good report.  She also had a normal echo with good ejection fraction.  She may go two days with normal blood pressure then wake up with it 198 over 101.  At least 2-3 days out of the week her blood pressure is over 180.  She takes Clanidine SP? then a zanix and it comes down to 130s.  We are considering sending her to the Mayo Clinic because we do not know what is causing this extreme high blood pressure.  How much can her heart and brain take of this?  She is only 58 years old and never experienced high blood pressure. Some doctors are saying it is anxiety which she does have but again she has had that her whole life and no blood pressure problems.  Does anyone have any idea what could be causing this and how much her body can handle of this.  When her blood pressure gets up she also gets dry mouth and her head hurts.  What should we do?  Has anyone been to the Mayo clinic?