Mercari Item Not as Listed

So, I'm kinda new to this in some ways.

I purchased a TTPD cardigan from Mercari that was listed as "like new". When I received it, there was a very large snag/pull on the back.

I messaged the seller and she immediately got defensive and said there are no defects in the photos of the cardigan. This is technically true, but in the photograph of the back, the sleeve is covering the giant snag.

I'm pretty new to Mercari buying, so what do I do? I told her that I would accept a partial refund or send it back for a full refund. I can fix the snag, so I don't mind doing that, but I also feel like I paid the price I did under the term of it being "like new", which it isn't. Obviously.

ETA - there were also some other defects that kept it from being "like new" imo, but one was pictured that I didn't notice originally. There is another small snag on one of the sleeve cuffs.