Thanks for the reply.
“Now alice can redeem this transaction by using her secret.”, that means Alice got the BTC right? So what stops Alice from refunding her ETH before Bob has the time to redeem? Because from here  I can only see a maximum time for refund. Perhaps there should be a minimum time for giving Bob the time to redeem right?
Also to be 100% clear here, ONLY Alice knows the secret initially and once she redeems then Bob will know the secret as well?