Molly Weasley had a vision. She wanted, all she wanted really, was One Big Happy Weasley Family. To that end, she felt no guilt at encouraging her youngest children in pursuing Harry and Hermione.
She got her wish. Ginny married Harry after the war, and Hermione and Ron married too.
But fate doesn't like it when you mess with her plans. Both marriages are disasters, but with magic, marriage is forever. Molly knows she made a mistake. Her son is an abusive little shit and Ginny is a spoiled brat who only thinks of herself and leaves Harry to look after their children. No body is happy with the situation, and it all culminates when Harry dies under mysterious circumstances and Molly is pretty sure it's Ron who did it.
She has to fix it. So, she goes back into the old family magic and finds a ritual that will take her back. Back before she used the love potions, back before she ruined her family.
Molly Weasley always gets what she wants. This time, she wants to make things right.