Hi,
Yes, changes in blood pressure with a pacemaker should alert you about the replacement of the pacemaker, because if your mother is completely dependant upon the pace maker for her heart beat, then this will affect her heart rate and hence the pressures.
It is necessary to consult a cardiologist immediately for a temporary pace maker, to support the heart rate while he changes the pacemaker. Hope this helps. Best.
It would make sense to think that it's caused by the need for a battery replacement, since the pacemaker is just that, a pacemaker and if it's not working, then her HR will be affected.
Hope this helps.