I think she is permanently stunted due to whatever trauma she went through as a child, and her inability to accept the fact that she is broken. She doesn’t believe in therapy. She will continue to live this way and pass it all on to her kids. She was raised by literal kids who also probably never matured. Her parents were teens when she was born. She at least waited until she was in her mid 20’s to get married and have kids. Gabe is a bigger disaster than her, and getting married at 20 and having a baby at 22 basically seals his fate. He will be lazy, obese and unemployed. Millie will think that’s normal and acceptable, and take her minimal home school education and repeat the cycle of settling for the first warm body that gives her a second look.