Yes write immediately, the words you used in your post here are factual, polite, and well-written. You could copy the same text, and send it to the seller. First, have in mind what you want her to do: do you want a refund or partial refund? Do you want to inform her for the purpose of preventing this from happening to another of her customers? I would write to her a first letter, informing her that you are currently washing the fabric AND WILL CONTACT HER AGAIN, once the fabric is washed, dried, and pressed, to determine if there is any damage..... Keep the lines of communication open, be direct, and simply ask for what you want. If you are reasonable; assume she will be as well. And good luck. Let us know how it all turns out. You will be doing her a good turn by communicating.