Hi Jo, you say she was full age at marriage so 21 or over that means she was born before 1889 but at least 10 years after your grandad? who was born in 1872, working out roughly between 1882 to 89.
You say she lived in Glenpark Street before she was married was her father still alive? what was his occupation? you could get someone to have a look at the street directories going back from 1910 Glenpark street for her fathers name at other addresses if they lived over in North Belfast going back to the 1880s then you know the parish and Area she was born then you can check with the parish reg or Proni.
Colette