She's such a careerist that she would betray long-time colleagues just for a promotion.

careerist 是由名词 career（职业、事业）加上后缀 -ist（表示"从事...的人"或"信奉...的人"）构成的名词，指"以事业成就为最高目标的人"，常带有贬义色彩，表示"功利主义者"或"野心家"。