Assuming that Ann is the d/o of Hugh (I presume you based this on father's name in her marriage cert ?) then Cronkbourne was the only industrial village on IoM (look up on www.manxnotebook.com) there was a considerable influx of northern Irish workers as they had experience in flax(or linen) weaving etc so possibly the Belfast link came this way

Euan = (like Scots Ian) is John in disguise but was anglicized to Hugh as the Manx language slowly died from early 19th C - Euan also spelled Ewan but the 'u' often appearing as 'v' was then treated as Evan (a common Welsh name) - if her gfa was Hugh and coming I believe from the north of the Island (sorry I strongly disagree with Donna re her suggestion) I suspect he used the Ewan form.

Did her husband die in Belfast or did the marriage not work out and she returned home? - she died at an early age usually such are in childbed but TB was also common in those days and in confined spaces could be passed between generations