if you look up graveyards on my ManxNoteBook site you will see that St Marks has its own yard.
(if you buy the Malew burials CD from IoMFHSoc think it is included on that) - no idea how imuseum have filed it - St Marks was strictly a chapel of ease to Malew (again a far amount of info on MNB).
re name she was I think baptised Walkinton her father I think Walkington - the name was probably not that well known in Santan being a Castletown name