The term "pig" is colloquially used to describe a man that looks at women purely as objects of sex. Is there such a term that describes a woman that looks at men purely as objects of sex?
Man-eater might work depending on the context. Also player.
If the woman is older and is interested in younger men, then the word cougar may be used.
Cougar is a slang term that refers to a woman who seeks sexual relations with considerably younger men. ABC News states that these women pursue sexual relations with people more than eight years younger than they are, while The New York Times states that the women are over the age of 40 and aggressively pursue sexual relations with men in their 20s or 30s. However, the term can also refer to any female who has a male partner much younger than herself, regardless of age or age difference.
(Canada, US, slang) A woman of middle age who actively seeks the casual, often sexual, companionship of younger men, typically less than 35 years old; by implication a female “sexual predator”.