I...need help appreciating the "I only have room in my heart for my child" trope because it makes no sense to me.
Most people with a kid have a partner. 90% of households with children in Japan are not single-parent (70-90 globally).
Like. Bazillions of people have room in their heart for a child and a spouse. Or two kids and a spouse. If she had a second kid would she not love them?
it's a stability thing I think. for her, entering romantic relationships, potentially breaking up, and dating as a whole means less time for her daughter and makes her daughter's life unstable.
kyou won't be going through breakups if she just doesn't date anyone
Am late, but what ziekang said, and imo because being in love and acting on it is another responsibility that would also affect her daughter, if not also another part of herself.
She has a responsibility to making sure her daughter has as stable of a life as she can give her, and adding another person into the family unit that encroaches deeper into their personal life is different from living with a landlord/ex-boyfriend. She can get distracted from fulfilling what she wants for her daughter if she allows herself to chase after a love that would affect how they would live, which would mean she wouldn't be able to keep her daughter at the forefront of her mind if it does come to pass that she's distracted.
Just because 90% of households are 2-parent household doesn't mean that that houshold started with the same situation as these characters. There is significantly more care that needs to be given to a change in environment and relationship outside of just "oh we definitely love one another, let's just get married and not think about what my daughter might think about it".