It's the seller's responsibility to get their item back in these cases.
If you don't she can escalate a case for item not as described, she'll get to keep the item and force a refund.
How ' faulty' is it? Entirely up to you, but she may settle for a partial refund, save you the journey if it's far ? She'll have to close the case first , for you to issue a partial refund.
@bonkers4bearsbitsnbobs