In "We Are Seven," the speaker of the poem and a little girl have an argument. He thinks that, since two of her siblings are dead, and four are alive, the kids in this family number five in all. She disagree, and says that her dead siblings count. They are seven.
In fact, what she says over and over again is that "we are seven." (Sometimes, she even exclaims it: "O Master! we are seven.") By titling the poem with the little girl's words (instead of, for example, the speaker's words, such as "ye are five"), Wordsworth seems to be siding with the little girl. The title reinforces the girl's point of view, not the speaker's. But is this enough proof to suggest that Wordsworth himself is on Team Cottage Girl? We'll leave that one up to you.