We don't see much of the Widow Douglass, but we get the feeling she's a nice lady. She takes Huck under her wing and promises to civilize him, which maybe not be what he wants but, by the standards of society, is a pretty nice offer.
Even though Huck doesn't much like getting "sivilized," he has nothing but praise for the Widow: she's "regular and decent" (1.2), she makes Miss Watson lay off him (1.6), and she doesn't lay into him when he fouls up his clothes. She even says that he's "coming along slow but sure, and doing very satisfactory… she warn't ashamed of me" (4.2).
We don't learn much about the Widow Douglas as an individual. She's a type: she's basically kind, mostly caring, and 100% committed to following the rules of society, from table manners to church-going to slave-owning. But is that good enough for Huck? Is it good enough for Twain?