I feel like part of Fate's character arc across the seasons is gaining the connections that she was denied as a child. Having Nanoha as best friend/lover was vital to her, but by this point she doesn't just have Nanoha — she has a mom, a brother and sister-in-law, a niece and a nephew, good friends, and three kids (maybe four, if you count Arf that way? It's hard to categorize their relationship).
She's come a long way from the child so alone that she built her own playmate. (Yes, that's not why she contracted with Arf, but...) I get the idea that she would still worry about going down Presea's path, were she to lose someone so vital to her, but the life she's built for herself is stronger and more connected than her mother's ever was.
