They might be talking of the fabric more than the pattern. I believe I'd sit down with one or both of them and a computer (or a couple of quilt shop catalogs). If you choose the computer, I'd search for images of vintage quilts and fabrics and get them to point out what appeals to them and what doesn't. There are so many words-- vintage, antique, retro, shabby,, old-fashioned--used in different ways by different people. If you can't meet with them, maybe they could send you some photos after searching the computer on their own.

I would ask them to send you some pictures of what they perceive as "Vintage"...but if she is about the age of my daughter and her friends then Mea(above) gave you good information. There are some who make quilts out of old sheets and pillowcases from the late 50's, 60's and some who use new modern style fabrics. Look at Denise Schmidt Heather Butler and my favorite is Zen Chic.

Can you explain to them how much work (and time and money) is involved in making a quilt - and that you want to please them - but need more guidance as to what they mean.

I think the suggestion to let them select from patterns that you are willing to make is an excellent one. Then have them go fabric shopping (or picking, if they are going to shop your stash) WITH you. Changing the fabrics can give a different look to almost any pattern.

At the very minimum, ask them to give you some color combinations they like (Also the combinations they actively dislike!) Sometimes the colors help determine the style.

'Vintage' to some people can mean from 10 years ago - and when one considers how fashions and colors recycle, similar styles could have been from 40 or 70 years ago!

I think this quilt is an example of one that seems fairly easy to assemble, but changing the fabrics would give it a totally different look.

quiltingboard.com/pictures-f5/if-you-like-soft-colors-one-you-hot-off-machine-t201434.html

I agree with most of the others who posted here. I would have them pick a pattern and suggestions for the fabric. My children's idea of vintage is from about 1960 and differs greatly from my idea of vintage (civil war). With all the time and expense you will be putting into the quilt, it needs to meet their approval. JMHO
Sue

Definitely 30's prints and the Dresden Plate is a nice pattern to use for these fabrics. Personally, I think any of the old time patterns would be nice; i.e., Churn Dash, Ohio Star, Irish Chain, etc.

I think scrappy string quilts appear to be vintage

Why not gather some pics from the Internet and ask them about the style they have in mind? The terms Vintage vs. old fashioned are pretty vague and mean different things to different people. Did they maybe think shabby shic? I remember seeing a room in a vintage shop in Manhattan decorated in French provincial style. What drew me in from the street was the quilt on the bed. It was made from a number of soft color floral prints on white (mostly pink and red roses) with a simple country pattern - one print was a 10" or so square of fabric, no cutting. In that room it was beautiful and effective and both vintage and old fashioned at the same time. Let them look at pictures of different styles, pick a color and save yourself a headache.

You definitely need more input from them. One of my daughter's was making a hand quilted quilt for her sister's wedding thinking she had chosen colors her sister would like. She visited the quilting sister who showed the top to her saying it was for someone else. She hated the colors and actually said it wasn't something she would like in her house. QS was angry and hurt. The quilt was finished and given to someone else. Her sister received a wedding gift of cash. Can't dislike the color of money.

Vintage to me would never mean the 30s. I'd check with them.
Vintage to me brings to mind repro fabrics - Civil War era etc.
If that's the route you wind up going there are lots available
Reproduction Fabrics, Vintage and Vogue to name 2. You can Google for other sources.