Hanks & Hodges's
A Dictionary of First Names gives Ciorstaidh, Curstaidh, Ciorstag, and Ciorsdan as Scottish Gaelic forms of
Christine or
Kirstin. Of course, it's quite possible that spelling in Scots Gaelic is not completely standardized, and thta Ciorstan has also been used.
I would think, however, that any of those forms who be difficult to pull off for a woman who did not live in Scotland among people familiar with Gaelic spellings -- though actually Ciorstan would be the best of those spellings if you had to choose one to give to a girl in another English-speaking country! :)