"And we've just talked for the first time today," she says, "and you're asking me to suck you off?"
You apologize.
"And look!" she teases you, "You said Sandy sucked your cock already, why doesn't she let you have an orgasm then?"
You confess that you don't know why Sandy just sucks and kisses your cock, as that just makes you more horny than ever.
"She's really got you over a barrel, doesn't she?" she says, laughing.
Yes, you agree; that's why you are so horny and frustrated.