Why don't you write back and tell specificially what additional supplies would be required and include a cost for labor. Don't use any of your supplies unless you have already told her. However, you should include the cost of supplies even if it is scraps from your own supply. You can use those scraps for your own projects and will have to eventually replace them. Do I understand that you don't have the kit. You might say that you are not sure about the time it will take but based on the information it will take approximately X number of days and the cost will be X.
I got myself into a situation similar to this many years ago and it taught me a hard lesson. It was an exchange situation - hand embroideried doll quilt for my granddaughter in exchange for finishing a partially made top which ended up being a queen size quilt with the purchase of additional reproduction fabrics and quilted.
If she is a real friend then she should understand.
But don't give in please.