When a girl smiles at a guy and then looks down it usually means she likes the guy or thinks he is cute, but is shy and maybe embarrassed. She may have a crush on the guy and want to go out with him, but feels shy and embarrassed when around him.
ummm, well, a girl could kiss a guy. A girl could flirt with a guy. A girl could hurt a guy. A girl could kill a guy (not advised). A girl could make love to a guy :P, a girl could - and this is the best of all - love a guy.