I don't think that Marisa did this out of kindness, but practicality. I believe that she's a sociopath - she didn't seem terribly upset to find the dead body of her father.
Yeah after reading the past page translation, seems like wandering around alone would have been a death flag for her, so she chost to have her mother along for the ride, or thats how I see it anyways, still a clever move though.
FORGIB MOMMYY...!I'M ZORRY LIDDLE ONE!I'M ZORRY...!dashbawlingYou remembered...!Little one...!when the little one was inside me...!This is what I sangThis song...!Yu~