Hit on

A: Cindy is lovely and laid-back. It’s surprising she doesn’t have a boyfriend.

B: That’s because she never realizes when guys are hitting on her. When they think she’s not interested, they simply move onto someone else.

Note: This is an American slang term for “flirting with or showing sexual attraction to someone,” dating back to the 1970s. For example: The women were all hitting on George, and he appeared to relish the attention.