。
She memorized the poem effortlessly.
Literal
She [topic-は] difficulty [even-も] without that poem [object-を] memorized.
苦もなく ('without difficulty, effortlessly') is a literary set phrase — 苦 ('hardship/pain') + も ('even') + the negative continuative form of ある, contracted to なく. The literal force is 'without even hardship.' 暗記 (literally 'dark-memory') is the standard word for rote memorization — committed to memory so thoroughly it's recoverable in the dark, without seeing the source. Memorization is culturally weighted in Japanese education, where students routinely 暗記 entire poems, pieces of classical literature, and historical dates as part of their schooling.