This study investigates how four female Mandarin Chinese-speaking L2 learners at a U.S. university engage with machine translation (MT) in English writing and develop strategies to manage its affordances and limitations. Participants completed both MT-assisted and non-MT-assisted writing tasks. Guided by Activity Theory, the study qualitatively examines MT as a mediating artifact that shapes writing processes through technological affordances, academic norms, and learner agency. The findings show that while most participants relied on MT for grammatical and lexical support, one learner critically evaluated its limitations and adopted alternative strategies, including peer feedback and writing center consultations. These results highlight the diverse and strategic ways L2 learners engage with MT and suggest that tensions in MT use can promote adaptive learning. The study offers pedagogical implications for integrating MT to foster learner autonomy and metalinguistic awareness.