Theory on Min Na Ang Yeon Jo o

my theory is   when Yeon Joo (fake Min Na  ) went to the hospital for her grandma  
Min Na saw her and made a deal with her to stay in the hospital instead of her
so Yeon Joo said yes because in that way she can stay with her grandma all the time  
thats why Yeon Joo is wearing hospital gown (PJ's)
What do you think ??