I take those kinds if orders all the itme, and have never had a problem. I understand the issues discussed above. Those are all good points. However I have several clients that send me fabric regularly. I do not place a label inside these dress and charge for the amount of time it takes me to complete. Make sure you tell them the amount of fabric you will need to complete the entire order.
It's a judgement call and you should do only what you feel comfortable with, but I thought I'd give you another view.