I'm sorry to hear about your friend. You may not understand the mechanism behind the funds transfer.

Bittrex, Poloniex, Binance, etc have accounts in which STEEM & SBD is transferred. This is how the STEEM is transferred to the exchange via those accounts. Each transfer has a unique memo assigned to it. This is how Bittrex knows which Bittrex customer account to deposit the STEEM.

This means that everyone that needs to transfer STEEM or SBD to Bittrex sends the currency to the same account (but with a different memo number).

By no means is Bittrex part of this scam.

What has actually happened is a scammer has taken your friend's SBD and transferred it to the scammers account on Bittrex.

I recommend that you send the info to Bittrex including the memo attached to the Bittrex transfer. This will link the scammer to the Bittrex account. Hopefully Bittrex will freeze the scammer's assets while it is on Bittrex.