Beth is a poem about a girl caught in an endless fall, and it's hard to tell whether the fall is literal or a picture of something inside her. Nothing in the text says what she is falling from or toward. We only get her fear. She feels lost, helpless, with "no one to help her" and "no end."
The form does a lot of the work. Short lines drop down the page like the fall itself, and the repeated "F" words (farther, faster, freely, falling, fading, forever) pile up and make the speed feel unstoppable. "Freely" is the oddest of them, since it hints at a strange moment of release inside the panic. Seasons blur behind her, so time seems to rush on while she can do nothing.
The mood is anxious and haunting. The final line leaves the reader unsettled: she can't tell whether she is simply falling or dying, and the poem never answers her.