First, I think you should consider how you feel about it. Thinking about the quilt and the amount of work you will put in, what amount would you feel good about receiving from this acquaintance for your work, above the cost of the materials?
After you figure that out, thoroughly itemize the material costs involved, add the estimated amount for your work (figured from above), then go to this person with these figures written down, and both of you sign the contract. Insist on the cost of materials up front, and don't start on the quilt until you get the money. When the quilt is done, she gets the quilt when you get the balance of the amount you've agreed on.
People have no idea what is involved in making a quilt, so you have to educate them beforehand. As far as what to charge, I can't help you there, as I've never made a quilt for pay.