This character is Carly also known as Jo!
This is Alexs late wife, She did pass away.
BUT i'm going to spoil somethings. Sorry not sorry,
She is a ghost, she is helping Katie and Alex get together because she knows that Katie would be perfect for her family.
Jo passed away from brain tumors.
At the end of the day Jo is helping Katie, Alex and her kids stay safe.
Jo warns Katie when Kevin has found her,
Jo is supposed to be living next to Katie but Katie doesn't realize that Jo really isn't there.