I find a Janet Cowie married to Robert Haldane and to them born a daughter Margaret Liddle Haldane in 1845 (Christened 5 April 1845) at Campsie, Stirlingshire.Janet Cowie and Robert Haldane were announced for marriage or married 29 May 1845 at Campsie and 6 June 1845 at Baldernock, Stirlingshire (after Margaret was born!)
This may be a clue as this Robert Haldane could be the grandfather of your Janet Haldane (if the Cowie name is a connection).
This is one of 2 Haldane/Campsie connections I find.
The other is Helen Cowie and John Haldane married 16 July 1752 at Alloa, Clackmannan, Scotland.They had several children.
I suggest you pursue marriage and birth records for the first couple (Robert and Janet) and see if it leads you anywhere.