Terry, I see that young Maud AVERY was born overseas - so perhaps the Avery's met Emily there, so she might have married and been widowed overseas??
Along those lines, and this may be nothing more than coincidence...
the 1851 census lists three Emily's born around 1841 +/-2 in Wateringbury. One of those is Emily MARSHALL, living with her Uncle Edward MARSHALL, an "Annuitant - East India Company". A possible connection? In 1861 she's a pupil at a "posh" school in Lincolnshire, perhaps the sort of place that would turn out Music Professors?
Of possible relevance - there is a death for an Emily CURTIS in Liverpool, Sep qtr 1888, age 49 (i.e born around 1839).