i guess 'lesson-learned'
if you wanted to 'sell' the fabric you should have already decided what you wanted for it before you ever offered it to her; offering it at this price...
since you let her just take it you may never hear from her again, but on the other hand she may surprise you and something may mysteriously show up. or she may months down the road need something else and contact you...at that point you could 'gently' remind her that you helped her once and she did not hold up her end so you either can not help her this time, or you can but have to be paid at the time of purchase.
you know,even if she had gone to a yard sale or thrift shop she would have been expected to pay before going out the door; letting her just have it seems like...you let her have it, without really expecting anything in return.