As the god of foresight, Vadderung always matches Valkyries perfectly to clients, probably without them even asking. Marcone needs efficiency and professionalism, so he gets the no-nonsense Sigurd. Lara would get bored with someone like Sigurd, so she gets the flirty, playful Freydis.
Bear is a more complex choice for Harry. He needs a powerful physical guardian, like Michael and Murphy rolled into one, but more importantly, he needs someone who is kind. He needs someone with a nurturing personality, who can push him when he needs to be pushed and comfort him when he needs to be comforted. He needs someone to remind him to eat and go to bed at a reasonable time. He needs someone with an immense physical presence, someone large and strong enough to dwarf him, so that when he breaks down, she can hold him and comfort him like a child.
In short, Harry needed a mother.
That's what Bear is to Harry. She's a maternal figure, something Harry has never had. He's had several father figures of varying quality, including Vadderung himself, but Bear is something new for him. She's literally a Mama Bear.
