I suspect Christian d age 42 in 1820 (buried Braddan 10 Jul 1820
Her age at death the fact that she (+ Wm were noted as both of parish at marriage) suggest that her parents might be Wm Christian + Jane Finch baptised Douglas St Matthews 17771116 but there are other Isabel(la) Christians baptised in nearby parishes who could match and Douglas was a growing town.
I think her last two children (of 8) Mary + Catherine died in childhood Mary age 8mo in 1817 and Catherine age 3 yr 5m in 1822

However can't definitely find Wm in 1841 (when he would be over 60) tho given several young children at death of wife I suspect he might have remarried

There are a couple I would investigate further tho the parish register are not help as Onchan gave no mother's names -- but possibly Wm is son of John Taggart + ?Mary Kerruish bapt Onchan 1773