I'm pretty sure she IS her granddaughter but she's resentful towards the grandma so she's trying to take her money. It made no sense why she's happy when her mom was "abandoned" by granny and they were left to fend for themselves. Remember JH says his childhood was horrible so I'm confused as to why she's so happy, or maybe I could be wrong maybe God has given her joy.
I'm confused as to why did SoMun friend cared to tell Mun Hana was out with a guy when he dose't even care.........."awwwww man they got me all excited, I thought I was gonna see a gaot"