Eight-year-old Abby is innocent in some very specific ways. It's rather like hanging out with a Disney Princess. We're watching an anime called Fruits Basket; it's fairly typical in content but has been rendered TV-PG by virtue of bleeping anything stronger than the occasional "dammit". Standards for what is acceptable in Japanese animation are somewhat different than Western ones though, and so phrases like "two-timing bastard" and occasionally even "shacked up" are common.
To Abby, the above phrase is a trigger for conversations like this one from the movie Enchanted:
She's definitely the Giselle in this sort of situation - and Giselle herself is an affectionate parody of the typical Disney Princess.
This attitude extends to real life too. Abby has a fairly encyclopedic knowledge of the female reproductive system. She gets why cycles occur ("egg goes from here to here and gets cushioned by blood to protect it and if it doesn't turn into a baby, it has to go somewhere and that somewhere is out") and knows about the difference between vaginal and surgical delivery. But as for how the egg "turns into a baby", she has expressed no curiosity.
And as her mother, I'm okay with that.