Posted: 01/04/2014 at 17:37
But she wants to keep it creamy pink!
Pink mophead macrophylla hydrangeas will stay pink on chalky soil. They will turn mauve/blueish if your soil is acid.
However, my guess is that your hydrangea isn't a macrophylla - it sounds like H paniculata 'Limelight' or similar - the lime content of the soil won't affect its colour.
Does it have a label?