1. The deadline is way short, too much pressure on you. See if you can negotiate this with her by including pictures of the fabrics and the design in a gift envelop so that the recipient can see what she'll be getting a couple months later rather than on Christmas Day.
2. You will likely have to purchase interfacing/stabilizer/something fusible for use on some of the fabrics, allow for the cost of this yardage in what you charge. This stuff ranges from $.99 to $5.29 at JoAnns.
3. As these will be used clothing, you may have to wash, dry and iron the fabrics before you can even start to cut and assemble. Allow for this labor.
4. Always include a thread charge, even if it is the cost of just one spool. In your case, a cotton wrapped polyester will likely be the best for mixed fabrics, just like general, all-purpose sewing.
5. Will the quilt be washed again after making it? Allow for that time and energy use.
6. Will you have to set aside other things you were planning to do for the holidays to take on this project? Consider that in your fee.
7. Will you have to drive to deliver it to her or will she come to you to pick it up? Gas fee.
I know I seem to be nickle and dime-ing this to death, but my point is to show that we often do not realize that there is MUCH more going into our "offer to help" than what we do at the cutting and sewing table. If you are being paid "just for your time", then consider ALL of your time put into the project.
Jan in VA