Leonie,
Tradition was to marry in the bride’s church, so it’s possible that Mary Elizabeth was baptised in Ahoghill Church of Ireland. If so you might also find any siblings she had. That church's records are not on-line anywhere but there is a copy in PRONI, the public record office, in Belfast. Their copy is not on-line and so a personal visit is required to access them. If you are unable to go there yourself, you may need to employ a researcher.
http://www.proni.gov.uk/guide_to_church_records.pdf
Ahoghill COI’s records start in 1811.
I looked for a death certificate for Abraham Wallace but did not find one. Nor is he listed in Griffiths Valuation, so that suggests he died before 1864 when death regsitration began. His burial may be recorded in the church records though. Ahoghill Burial records start in 1821.
Gravestone inscriptions in Ahoghill and the surrounding area are listed on this site:
http://thebraid.com/genealogy.aspx
I don’t see a grave for Wallace of Gracehill but there are a couple of stones in one of the Ahoghill graveyards that just have the surname Wallace on them, and no other details, so who knows who they contain. (The church is unlikely to have full details of who is in each grave from the 1800s).
Only wealthier people could afford a gravestone and the majority of the population were buried without one. Farmers and tradesmen often had a gravestone, agricultural labourers, weavers and others like that did not.
I live in the Gracehill area but have not heard of anywhere named Cold Spring. Gracehill is not a very big village). Is that information on the 1853 marriage certificate? If not, what townland does it give for Mary Elizabeth’s residence? Also, what does that certificate say Abraham Wallace’s occupation was?
