I wonder that too ... the thakurain definitely seems to have a very soft spot for Paro ... Paro and Bindi went to the thakur's house before returning to their own home after the desert incident ... and the thakur said that his wife was even happier than Paro herself about her wedding.
Maybe the thakurian and Paro's mother are sisters, or Paro's mom was the thakurain's close friend. Mother's close friends are often called maasi .