Nana K was incredibly selfish in the decisions that she made.

Especially in deciding to keep the baby. She didn't even think about the wellbeing of the baby itself in making this decision.

Here's the biggest reason why: During the conversation with Junko (when Nana K was confused whether to keep the baby or not), Junko asks Nana if she'll be okay even if Takumi doesn't end up loving this kid and she quickly nods there. Even after being in the company of all the people whose family either didn't exist, or didn't love them - like Shin, Nobu, Nana etc. she learns absolutely NOTHING that absence of parental love can be absolutely damaging for the kid. And a single parent can absolutely never fulfill the role of the missing parent.

This is further made true when the kid that she wants to bring into the world, will have a father who absolutely doesn't love their mother and even assaults her as per his wishes.

She said to Junko, that in the clinic it became clear to her that she had to get her act right, and that she realised that she needed to act mature after the gravity of the reality dawned on her, that there was infact a life inside her.

Apparantly her 'motherly instinct' also came forward because of it , so much so that she even empathised with Nana O's mother who was a very poor parent, and because of which Nana O had definitely suffered all throughout her life. This expression of empathy and understanding regarding the reason Nana O's mother gave birth to her, was not an attempt to actually understand the reason or the consequence of that decision in the life of such an important person to her , but rather an attempt to bring legitimacy to her own emotions by seeking conformity in someone else (Nana O's mother in this case)

Junko asked Nana K to be a mother like her own, and Nana K expressed willingness for it. But she fails to consider that she can never be that mother of her child because she was ready to bring that child in a house which would never feel like a home.