Look at the witnesses on the marriage entry, sometimes it is a close family member or parent who signs as witness.

If the couple who married stayed in the area then look for their burials or burials of any of their children who died very young. Then see if other families of the same surname are buried in the same Churchyard/Cemetery and if any headstones exist as these often mention relationships.

Or as John has said trawl through baptisms, not all indexed so if might mean browsing some on Findmypast, in Devon FHS Members' Area where there are images of Parish Registers, check BT's on FamilySearch, again not sure if all have been indexed. And then you have the odd few Parish Registers that are not available online as the incumbent didn't give permission for them to be filmed, also some PR's haven't survived or been deposited with a Devon Record Office for certain dates.

Census records if she was still alive after 1841 should help with County and place of birth. You can then start a search in the parish she gives and if nothing broaden your search to surrounding Parishes.

Also worth checking Non-Conformist Baptisms