。
She might come.
Literal
She [topic-は] come might.
The minimal-form-of-uncertainty sentence. ~かもしれない literally decomposes as か (the question marker) + も (also/even) + 知れない (negative potential of 知る, 'cannot be known') — 'it cannot be known whether or not.' In modern usage it's a fixed unit meaning 'might, may.' Casual speech often shortens it further to ~かも. Note that the verb 来る comes in plain dictionary form before かもしれない — this is one of the patterns that attaches directly to plain-form predicates without any intervening particle.