Alyssa (Novel Series)

Alyssa is a Woodbury citizen mentioned in The Walking Dead: Descent.

Post-Apocalypse
Nothing is known about Alyssa's life, except she is 3 to 12-years-old.

Pre-Apocalypse
Alyssa is seen with Barbara Stern, and she babysits him along with other children.

After the destruction of Woodbury, it is very likely she is one of the few surviving children that made it out.