A friend asked for my Bitcoin Cash address to send some BCH, but after giving her my Bittrex Bitcoin Cash wallet address she instead accidentally sent Bitcoin and not Bitcoin Cash from her Blockchain.com wallet. Of course the transaction has not shown up and she is now missing her Bitcoin. She and I have both emailed Blockchain.com Support and they have been unresponsive in helping to recover her missing Bitcoin so it can be sent to the proper address. Any help anyone may have is Greatly needed and Appreciated!! These mistakes can be very costly as Im sure, whoever may be reading this, already knows!! Thank you Anyone and Everyone for your time and support with help on this issue!! Again, The Bitcoin was sent from Blockchain.com's wallet to a Bitcoin Cash wallet on the Bittrex exchange..... I have reached out to Bittrex customer support as well but still awaiting a reply! If recovered before someone has a chance to offer help, I will update this post with how it was done, but any and all help is GREATLY Appreciated!!
BTC and BCH have compatible keys. Bittrex holds the private key to the BCH address, which they can use to retreive your BTC coins. For how you should proceed, see here:
Unfortunately, once the transaction is confirmed on the blockchain there is no way to retreive the funds and, that I know of, there is no way to zap the pending transaction from the distributed mempool, nor can I imagine a way. The transaction will likely be confirmed in due course.
Even if Blockchain.com zap the tx locally and the Bitcoin show up again in your friends wallet, once the transaction confirms on the blockchain the outputs used to create the transaction will be spent and that Bitcoin will not be spendable. This also protects against double spending.
The one possible solution to this problem is if your friends Blockchain.com wallet allows RBF (replace-by-fee), you could conceivably (and I do not know how granular transaction control is with Blockchain.com) replace the original transaction with a transaction paying instead back to herself and with a higher fee. A few caveats, RBF is opt-in and so would have to be enabled on the original transaction, Blockchain.com needs to have the user functionality necessary to do this and, once the original transaction is confirmed it is game over anyway.