She's human, so she wants to live as a human—not as an immortal. She'd probably hate him for having to keep living and not living her life as an ordinary human. Therefore, Chrono won't be lonely with a child, because the child will have a part of her, and he'll still be able to see her in it, even after her death. Chrono will see a semblance of her even after their child has children, and so on and so forth.
This is what love is about. She wants to keep loving him and being with him but as a human. Spend her life and end with him as a *human*.
I will just use other manga as example, in Delicious in Dungeon there's whole country of human that become immortal they're so sick of it that even the king killed himself by going outside of "magic barrier". With similar logic, Minerva might just lose her mind if she keeps on living without ever see her child born or growing especially since she wants family not just Chrono, and as she said might hate him for it so she choose the brief moment of human life while leaving something behind. It's basically classic human value of "glorified death" in universe with huge different lifespan.
guys can someone please enlighten me on her logic? i just dont get it like she says she doesnt want chro to be lonely thats why she wants to have a baby. but idk, cant she just live with him forever if thats the case? is it because she doesnt want a time to come where she hates him after living for so long if she becomes immortal? but if thats the case, then isnt she a coward and why be in a relationship with him? idk guys pls take this with a grain of salt i've never actually liked soneone so i dont really know shit :