First of all Lafferty, or any variant of it (McLaverty, McLafferty, Laferty, McClafferty etc.) are all northern Irish names, by and large coming from present day Northern Ireland, in counties such as Derry and Antrim and from present day Republic of Ireland (but a geoprahically northern county), Donegal.
Go to www.irishtimes.com and to their "Irish Ancestors" section and see the breakdown by county of this surname and its variants.
Having said that, I've delved a little deeper and the only exact match I get for a Sarah Lafferty was from Co.Derry in 1852 but her father is not listed as Hugh.
However, a Sarah Jane McClafferty was born in Derry in 1854 with a father Hugh ... my source for these is www.rootsireland.ie which unfortunately is a pay site that they've recently restructured much to everyones disappointment.
Not saying the above are your ancestors, but the name is definitely northern, so hopefully this points you in the right direction.