This woman was the mother of Kayoko Kotohiki. She was the mistress of Kayoko's father but due to his status as a banker and husband, he couldn't be there for them. In order to make sure they were okay, he set her up to run a bar so they would have money to get by.
Kayoko's mother would try to rise her in a way where she wouldn't end up the same way so she gave her advice on attracting boys. It was her idea for Kayoko to get involved in flower arranging as she believed it would attract a nice boy. She would sometimes let Kayoko help run the bar in cases of emergency.