14th: Who is Sylvia (Isabella)?

After I thought I'd done enough for the day on bringing William McGREGOR's family a bit more up to date, I remembered that I'd spotted a William HENDERSON, blacksmith, living nearby in one of the Waterloo, Ontario censuses.
Unfortunately, he wasn't a wonderful lead into a hitherto unresearched branch of my blacksmith HENDERSONs from the Bridge of Allan (unresearched because to date other than my James, and William's Margaret, they are resisting attempts at being found). His parents turned out to be Hugh HENDERSON, shoemaker, and Marion GILLIES, of Kilmarnock, Ayrshire.
But in finding which census it was, and rechecking it, I also resolved a little niggle at the back of my mind in that William's household was enumerated as 1 male and 1 female, and I'd not noted the female member of the household, other than noting whoever she was, she wasn't a McGREGOR.
Closer inspection of the squiggle made her an Isabella HENDERSON, aged 18, unmarried, born Scotland, and living in Galt, Waterloo Co, Ontario in 1861.
So she is the next mission.
I've reloaded William McGREGOR's page, to show her in the household.