The GRO website gives us four immediate possibilities for her birth with 1877 +/- 2 years-
1875 - mmn KEARNS
1876 - mmn DALEY
1876 - mmn HERON
1878 - mmn HOOLEY
Not immediately seeing an obvious marriage.
I also looked at deaths 1879 +/- 2 years for Manchester, looking for a woman of the right age but I can only see infants and people over 50...
Edit- with alternative spellings, a few possibilities:
CONLEY, MARGARET 29
GRO Reference: 1877 J Quarter in MANCHESTER Volume 08D Page 213
CONNELLY, BRIDGET 28
GRO Reference: 1879 D Quarter in MANCHESTER Volume 08D Page 167