Customer transferred extra money then I expect

[anhminhngo]

What can I do when my customer by accident she sent me $5000 instead of $500. She asked me to help her get $400 for Steam Card and adding with my sneaker that she wanted to buying from me from eBay. She was email and asked for offering. First time I got wrong $400 gift cards then I went back to buy $400 Steam Cards for what she after. I sent email for PayPal to confirm my Steam Cards so I can receive money from her. Some how by mistake and missed understood. She was sent me extra $500 but become $5000 for Steam cards. I don’t have anything to give her that $5000 Steam cards. And now PayPal sent me warning messages

[kernowlass]

@anhminhngo 

You are being scammed, no funds in your paypal balance means you have NOT been paid.

And paypal do not get involved in upfront fees or sending gift cards.

She is now trying to scam you into sending a refund for funds you have not received yet.

[anhminhngo]

What can I do right now