If the combination cylinder is on the same floor as the bathroom I find it hard to understand why she was getting good preasure before the new taps were installed.
Measure the static head from the floor to the water level in the cylinder then measure the height from the floor to the outlet of the tap.
The difference will give you an indication of the preasure available.
10m static head = 1 bar give or take so if the cylinder is on the same floor there can't be much between them.
(IS IT A COMBINATION CYLINDER)
