Not forward but reticent or reserved in manner
Given to flirting
Your buddy is being a little coy but he's hung around the wrong people long enough to pick up some information.
She gave him a coy smile.
She looked at him with a coy smile before approaching.
Carmen smiled in a coy way and leaned toward him.
When he shifted, Jen leaned away with a coy smile and trailed the finger across his lower abdomen, moving around him.