Jake's mother is an unseen and minor character in Flight 462.
Nothing is known about this character before the apocalypse, except she was bound for Phoenix on Flight 462 and was unable to board the fight due to the last seat been taken.
Jake's mother made her first (and only) appearance in Part one of Fear the Walking Dead: Flight 462 as a voice on the phone. She tells Jake that she wasn't able to board the flight and she will join him in Phoenix. She doesn't seem disturbed by the screaming Jakes in the background of her call.
It is revealed by Alex that Jakes mother was unable to board the flight because she (Alex) took the last seat.