Mrs. Grant is one of the most easily likable characters in the book. Even Fanny, who often silently judges people, can find nothing but nice things to say about Mrs. Grant:
Mrs. Grant was of consequence; her good-nature had honourable mention – her taste and her time were considered – her presence was wanted – she was sought for, and attended, and praised [...] (17.6).
But Mrs. Grant is more than just a friendly neighbor. She's also a person with some interesting and positive life philosophies, that we hear in her conversations with her younger half-siblings, Henry and Mary. Discussing homes and marriages with Mary, Mrs. Grant notes that they both have good and bad aspects, and people just have to look on the bright side and not have overly high expectations. If more characters in this book adopted Mrs. Grant's point of view, there would be a lot less drama.
Depend upon it, you see but half. You see the evil, but you do not see the consolation. There will be little rubs and disappointments everywhere, and we are all apt to expect too much; but then, if one scheme of happiness fails, human nature turns to another; if the first calculation is wrong, we make a second better; we find comfort somewhere – and those evil-minded observers, dearest Mary, who make much of a little, are more taken in and deceived than the parties themselves. (5.25)
Mrs. Grant often makes some of the best thematic statements in the whole novel during her conversations with Mary. And she's not some sort of Pollyanna optimist either. Rather, Mrs. Grant has a positive, but still realistic view of the world.
She's older and wiser than Mary but she doesn't try to boss her or Henry around. Arguably, both Henry and Mary probably could have used some stricter guidance, but Mrs. Grant definitely provides them with a better environment than their previous home, and she offers up good advice without forcing it down anyone's throat.