The title, "zeugma," is the key to this tiny poem. A zeugma is a figure of speech where one word governs two things in different senses. Here the verb "tripped" does double duty: she tripped into her feelings, and she tripped on the stairs. One small word joins an emotional stumble and a physical one.
The poem is about a woman who gets suddenly overwhelmed by emotion and, at the same moment, falls. The speaker watches from the outside. We get no description of her face or what she feels, only the quick, almost flat remark that "she's probably fine."
That last line carries the mood. It sounds casual, even a little dismissive, but the word "probably" gives away some doubt. The speaker seems to hope she's okay without being sure, or perhaps without wanting to look closer. The tone mixes dry humour with unease, and the short lines leave a gap where the real feeling might be. Like a fall, the poem is over before we're ready.