Horniness / Arousal
“Horniness” is a colloquial term for strong sexual desire or arousal. “Arousal” is the more general and neutral term, describing a state of physical and/or psychological sexual activation. Depending on context, both terms can sound neutral, familiar, or crude.
The sentence “The better the foreplay, the hornier the woman” is not a useful general statement. Sexual arousal varies from person to person and is not tied to a particular gender. It depends on many factors, such as mood, trust, physical condition, context, and consent.