Favour to ask then from you or anyone else in Hong Kong. Could you do a test transfer to my wife's gcash account? Only needs to be a minimal amount.
PM me for her details
From the UK I know the Sendwave app allows sending direct to gcash, let me know if you want to try a test send. I have an offer code that adds £10 to the transfer, so send £1 I receive £11
The Hong Kong HSBC account is agreed so that is another option.