Look for birth and death records for each of her children; full names of mother are often listed on death certificates if known by the "informant" -- the person providing the information.
Similarly, some (but not all) marriage records list the names of parents, so look for marriage records of each of her children. Remember there's a difference between civil marriage certificates and church marriage records. Each may have different information. (Ditto with births/baptisms.)
Just because you can't find their marriage record doesn't mean they weren't married. What do you know about their religion? Or where they went to church?
I have an 1867 New Orleans birth record that says my gr-grandmother was the lawful issue of her parents. That means her parents were married, but I can't find their marriage ANYWHERE. (This is the couple who were probably married at a Catholic church, and I can't request their marriage record without knowing their address, and I don't know their address...)
See how I've documented this problem/challenge; maybe you'll get some other ideas: