Usually, when someone is on the charm offensive, they tend to exclude or ignore others in order to channel all of their social energy in on one person, who they have designated as their goal.
The term can also describe female behavior towards a man.
Ricky's Mate: Yeah, he's on the charm offensive for sure
2. Peter: (To Ricky) Sorry i didn't really catch you last night, i was on the charm offensive
Ricky: Yeah i could tell...I doubt you got lucky though- misdirected energy really..