Because, apparently, in the comics she became a nun after she left (due to postpartum depression/psychosis), and we see Jack talking on the phone to someone who is presumably her and asks her to take care of Matt, and next we see Matt after Jack's death he's at St. Mary's.
One of the nuns at St. Mary's is Matt's mother
Because, apparently, in the comics she became a nun after she left (due to postpartum depression/psychosis), and we see Jack talking on the phone to someone who is presumably her and asks her to take care of Matt, and next we see Matt after Jack's death he's at St. Mary's.
....so.