I have Alice Bradford Mitchell marrying Watson Emery Plummer 4-Oct-1864. No children listed, but...
Now I find a census household sheet from 1880 that lists very interestingly:
Charles P. Wiggin, Self, 52, Fire & Life Ins Agent.
Alice B. Wiggin, Wife, 38, Keeping House
Harry W. Plummer, Son, 14
Hazen M. Plummer, Son, 13
Annie Bell, Other, 21 (Irish Maidservant probably)
Your grandmother it seems, hadn't been born yet in 1880
Hope this helps a bit.