Now you see her, now you don't, because Florimell doesn't remain in one place for very long. Spending the majority of the first half of the poem fleeing from everyone she comes across, she's less of a fixed character and more of a mirage, since "nothing might relent her hast flight" (III.iv.39)—literally.
But don't be fooled, just because her appearances are brief, it doesn't mean they aren't important. Florimell is so beautiful that almost every single male character in the poem spends some period of time being in love with her. Florimell, like many female characters in the poem, embodies chastity, but unlike Britomart or Belphoebe, Florimell manifests her chastity less by fighting than by running.
Florimell relies on her ability to remove herself from compromising situations as a way to prove that she is chaste. It's only the god Proteus, fittingly shifty himself, who is able to pin her down and make her his captive for seven months, where she again proves that she is chaste by refusing his persistent advances.
Though many men love Florimell, Florimell loves only Marinell, ironically the only knight in the entire Faerie Queene who doesn't return her affection because he's vowed to love no woman ever. But in their mutual desire to remove themselves from the company of everyone, they ultimately make a good match. Florimell's name, which suggest "flora"—"flowers" and earthly nature, nicely compliments Marinell, whose name suggests the sea.
It's a strange fact of the poem that we in some ways spend more time with Florimell's evil duplicate, the False Florimell, than we do with the real Florimell. The False Florimell, crafted by an evil witch in Book III, ends up being the main star of a huge tournament in book four, and is passed on from knight to knight as men become obsessed with her thinking she's the real deal. But in exact inverse to the many men the real Florimell avoids, the False Florimell gets with a bunch of them: she is totally devoid of the chastity that defines her counterpart.