Hi - I thought that BL's index didn't have an age for Selina? Was it given as 70 on the full burial record?
When I saw Brian's index and that she was still alive in 1901 I had a look at the 1901 census where she was aged 76, widow, b.England, living at "(Widows House) Cambrian Place", Douglas.

I saw that Philip Cain family but discounted the Wm as being your one - possibly because he was still at home in 1851 - but I'll recheck. By the way Philip won't have been given as his father, or Mary his mother, or others as their children, because no relationships were given in 1841.

Sue