Hello,
on the 1851 census I have found an ancestor of mine who was employed by William, her name was Mary Wyllie. By 1861 she was a dairymaid at another Fenwick address, but we believe she had had a child by this time, which was why she was no longer living with William Orr and family.
She later married George Mair of Barneight, Mauchline, but gave her name on censuses after that as Mary Orr Wyllie.
I would love to know why she added Orr to her name!