。
She has completely stopped crying.
Literal
She [topic-は] completely stopped-crying.
泣き止む is a transparent compound: 泣く ('cry') + 止む ('stop / cease'). The two verbs are joined at the verb stem 泣き plus the second verb in plain form — a productive pattern across Japanese for forming compound action verbs. 止む specifically describes natural/spontaneous cessation (rain stopping, wind dying down, crying tapering off), distinct from 止める ('actively bring to a stop'). すっかり ('completely') reinforces the completeness of the cessation: not just slowing, but fully done.