Yes, you most certainly should be worried on her behalf, because it poses a great risk to her life.
Ignore all the 'thumbs down' I get for this answer from doctors, nurses, and medical students, "para-medics" and boy scouts, because the evidence is absolutely clear.
So is the theoretical case and so too is the substantive evidence.
I took them after my by-pass graft and they nearly killed me. I took myself off them (against the doctor's insistence) just in time.
They killed both of my next-door neighbours, within 6 months of each other.
I wouldn't let the doctors loose with beta-blockers on any friend, relative, or any frail elderly person.
If you're in any doubt, then Google "Dr. P.J. Devereaux". and read his conclusion that possibly 800,000 deaths (Canada) were directly attributable to the inappropriate medication with beta-blockers, after cardiac surgery
EDIT : P.S. Regarding the other postings, beta blockers are dosage-neutral. That is, the pulse-rate lowering effect is effectively independent of the amount administered ("The ABC of Hypertension" by Prof. Beevers, [published by the British Medical Association}.
So lowering the dosage is a waste of time.