Mrs. Partridge is Margaret Cadaver's blind old mother. What she lacks in eyesight, however, she more than makes up in insight. Mrs. Partridge has the remarkable ability to read other people and the situations in which they find themselves.
As is often the case with people deprived of one of their senses, Mrs. Partridge's other senses work incredibly well. Just by the squeak of someone's shoes or their particular smell, she's able to tell quite a lot about them.
Despite her blindness, Mrs. Partridge is still able to write. If her daughter finds a nice uplifting phrase or saying in the newspaper —such as "Don't judge a man until you've walked two moons in his moccasins"—Mrs. Partridge writes it down and puts it in an envelope which she leaves on Phoebe's porch.
When Phoebe finds out that Mrs. Partridge has been leaving the messages, the old lady explains that she thought they'd be a nice surprise for her, kind of like fortune cookies, only without the cookies.
The latest message, however, the one we saw earlier—"Don't judge a man until you've walked two moons in his moccasins"—isn't a surprise, nice or otherwise. Unfortunately, as Phoebe points out, Mrs. Partridge had left it on her porch on a previous occasion.