Please help! Is this a scam?

I agreed to list some items on EBay for somebody. He had some expensive jewellery items and needed somebody with a selling record on EBay to list them for him. A pair of earrings sold for £2,500 and the buyer sent the money to my PayPal account. The buyer then started to say that the guy was a scammer and he had copied the photos and listing description from another Ebay listing. She said she wanted proper photos of the earrings or a refund. I asked the guy (Simon) and he told me the earrings were already shipped. He sent a tracking number for the website: intfrefor.com which I then sent on the buyer.
She began saying that the website is fake and that he created a fake tracking number with fake information. I'm not sure what to do. I haven't sent him the money from the sale yet. I'm worried that if I do and the earrings turn out to be fake I will have the refund the buyer myself and I don't have the money for that.

Can somebody please help me? I really don't know what to do - I'm not sure if the buyer is overreacting or if this guy is a scammer.

[AlanJones]

It's a scam, no legitimate seller would trust a 3rd party to list items for them, only scammers do that as they've got nothing to lose. The website intfrefor.com doesn't exist. If that is the correct domain then that's all the proof that you need that this is a scam.

If you don't refund the buyer then they are just going to initiate a claim with PayPal, and when they do you are going to have no proof that the item exists or that it was shipped.

Can you please post any email addresses and / or contact phone numbers this Scammer is using ?

Thanks