Courage of the Heart is very rare

Bulma
Dragon Ball
Guuuuuurl - okay no not exactly that. But the fact that Bulma is a mature (as far as Brisby knows) woman, currently a mother, but still young and not quite middle-aged? It's amazing, to Mrs. Brisby, who is sorely lacking someone in her "age" group. Maturity group. Something along those lines. However, Bulma sometimes startles her with her completely desensitized reaction to violence...

Equius Zahhak
Homestuck
He's Gamzee's beloved person. There was a temporary confusion about gender and sexuality, but Mrs. Brisby was quick to get over it. How happy he makes Gamzee is very important to her, and because Gamzee loves him, Mrs. Brisby is ready to welcome him into the 'family'.

Gamzee Makara
Homestuck
Oh, Gamzee... he has perhaps the most important relationship with Mrs. Brisby. For a mother who's been separated from her children for so long (especially considering how short her life is!!), having someone to care for is something she really needs. He's in no way a replacement for her children, and though he is filling up a part of her that's missing, he's not just pointless filler. She genuinely worries for him, and teaches him, and... well, loves him. If asked, she'd say without missing a beat that Gamzee is a son to her. Is her son. She might hesitate to say it in front of Gamzee, but she would never be able to deny it.

Karkat Vantas
Homestuck
He is the grouchiest child Mrs. Brisby has ever met. But, at the very least, there are moments where they can get along with respect for one another. Though she (rightly) suspects that he's not very respectful of himself. Though she is not one to consistently meddle with Karkat's affairs, she does like to check in on him, knowing that he's fairly important to Gamzee.

Maka Albarn
Soul Eater
A very interesting and sweet young girl! She's only just come to meet her, but she's relieved to see a well-mannered girl for once. If only she knew. Still, Mrs. Brisby enjoys more than anything else, being able to freely talk and gossip like a girl with another girl. Even if Maka is very bookish, and much smarter than Mrs. Brisby is.

(N) Natural Harmonia Gropius
Pokemon
N is a very dear friend to her. Though they don't talk very much, N has helped her free mice from the pet store, and she has tried to perk him up and make him feel better. His strong bond with animals is what brought N to speak with her, and perhaps Mrs. Brisby's slightly more human disposition can help him grow more familiar with them. Though he is gone, she has not forgotten him.

Okumura Rin
Blue Exorcist
A hooligan, but still a boy with a good heart. Since the word "demon" holds no meaning to Mrs. Brisby, she's perfectly unaware of any reason she should have to be wary of him. Well, more wary of him than she is of humans in general, at least. She's keeping an eye out and policing his language, but now that he's dating Maka, she's certain she doesn't have to worry too much. Maka is such a sweet girl, surely she can rangle a rascal boy in? Teehee, young love.

Zelos Wilder
Tales of Symphonia
He's strange, and quite a ladies man, she can tell. But he's not disrespectful to her, which is really all she asks. He's become quite a good friend of hers... after all, it's much easier to tease with him and gossip than it is with most others! She sees him very much as a good friend, though she's yet to feel close enough to do much more than offer simple advice for what ails him. Likewise, he isn't quite close enough to trust her with many secrets, and she understands perfectly and doesn't begrudge him a bit.