"Hey is this ____"
"Ian gave me your number" (maybe add "he said you could get me green")
(pause to let her say something, like 'oh yeah i got what you need' just to make sure your on the same page)
"What can you get me for $40"
(ask that instead of "i need a 40" because that could mean something different and more potential to get ripped off, KNOW what you are getting before hand. weight, quality, price, etc.)

Then once you break the ice the convo should carry itself, dealers aren't new to this and they know how to set up deals, so don't worry. Just make sure you cover key points, like how you got the number and what you want, and what they can do for you.

She'll probably do most the talkin' for you. Just ask the questions you want to know.