。。
She still isn't here. I think she might've gotten lost.
Literal
She [topic-は] yet not-coming. Road [at-に] got-lost [explanatory-の] might [quotative-と] think.
のかも知れない adds the explanatory nominalizer の inside ~かも知れない, giving 'I think it might be the case that she got lost' rather than just 'she might have gotten lost.' The の frames the supposition as an explanation for the situation at hand (her absence) — slightly more reflective and reasoned than the bare かも知れない. 来て in hiragana (きて) is a stylistic choice; the kanji 来 is everyday and the hiragana version reads as light, conversational, or reader-friendly.