All we know about her pre-zombieland past is that after she graduated from college, she worked as a clerk at a law firm.
She was on a road trip with her sister Amy when the outbreak happened, where they met Dale and The RV That Shall Never Die. Maybe that law firm was in L.A.?
Maybe, just MAYBE, she was the ex-wife of Travis (Cliff Curtis), the star of FTWD, and the mother of their teenager. She has pretty bad luck with men, too. so yeah there's that. The timelines and ages probably don't match up at all, but who cares? Do you want to see Andrea in Fear The Walking Dead