I know a girl called Siobhan from Donegal who also pronounces the bh as a w. Everyone calls her shevaun and she doesn't correct them, but at home she's called shewaun. The oo and i is probably just your granny, but Irish still has a lot of dialectal variation. In the south, 'how are you?' is 'conas a ta tu?', but in the north it's 'cad e mar ta tu?' (k'jay mar tah too) - quite different.