Sweater is much smaller than described in listing. What rights do I have?

[flashanddash]

I bought a sweater from a US seller, and took notice of the measurements in the description.  Yesterday the item arrived and it is much, much smaller than the description states (ie bust measurement is meant to be 47 inches, it is actually about 41, sleeve length is meant to be 18 inches, it is actually 16 at the longest part, 15 in other parts, making it far too short for me.  Also, far from being the plush mohair of the description, it is actually quite matted and flat from how it's been washed.  I have contacted the seller, who says it can't have been washed badly, as it would then be out of shape and faded (not true!) and has asked me to send photos showing the garment next to a tape measure, to prove what I'm saying.  I'm happy to do that, it sounds quite reasonable as she doesn't know if I'm trying to pull a swifty, and I have requested a full refund.  Now, my question is, can I push for a refund of the postage too?  I would never have bought the item if it had been properly described, and don't see why I should be out of pocket for return postage of a thick jumper to the US when it actually was not my fault in the slightest.  Do I have any rights with ebay?  Thanks in advance for all help.