Keep this between us or You know what I mean are my best guesses.
What does it mean when a woman gently hits a guys upper arm after telling him something?
Most of the times that she tries to get your attention, she tries to create a connection or she try to tell you that she is interested in you.
Girls do that all the time with me but it doesnt mean they like me in that way , its just human nature to tap someone after sayin something to want a reaction out of you/of if you're listening.
It means they are flirting with you and trying to get your attention and maybe some sexual fun after.