Get all the numbers from the designer including sizes, quantity, print surfaces, etc.
Unless the designer is connected with a good printer or lab, it may be best to simply supply her the prints.
I've worked both ways, some requesting a file for x-number of smaller prints, others wanting prints for framing and the latest wanting canvas which will be laminated, dry mounted, framed and delivered for installation to the client.
If you are supplying the prints, you'll need to figure your time in preparing the file, a royalty per print and the cost to produce that print plus mark-up for your handling the job.
If it's just a few prints, cost/print is higher. If it's for a whole bunch, the price/unit goes down because your are dealing in volume.
A similar project to yours that I'm nearly closing started negotiations in May and we're close to signing. Phase one of several will require nearly 300 18x22 to 28x40 prints on canvas. Because of the time this has taken, it has given us the luxury of taking our time to research the materials, techniques and workflow to maximize our efficiency and make a reasonable return on our efforts. We were able to find material that will allow us to do a lot of our own production in-house rather than farm it out, thus cheaper to the client and better quality with better control for us and more $$ in our pockets.
Sit down and get all the info and let it sit then take another look. Approach it holistically and look at all the angles see if you can make it a win-win-win. Pricing is perfect when you hear them sucking air, too low if they grab it quickly and too high if they say "sorry". With that, have a fall-back plan asking what can you afford and working down from there...