The “D” in Claritin-D is pseudoephedrine. It falls in the class of drugs called sympathomimetics and these can aggravate existing high blood pressure. She may want to give plain Claritin (the antihistamine component of the drug) a try, as antihistamines in general pose no problem for those at risk for high blood pressure.
There is no ready explanation as to why Flonase seemed to cause panic attacks and heart palpitations. Maybe the two just seemed to be related.
Good luck