Your wife is not permitted on the departures side. She lacks a same day boarding pass. Thus, not possible.

You can do it alone, but as stated above the practice is being cracked down on. People have reported 30+ minute waits to get taken back out from the departure lounge to arrivals area.

Fwiw, I have confirmation from HKIA that they have intentionally slowed the process because people aren't supposed to be doing this. Although it is very hard to prove people don't have a legitimate reason.

However, this isn't even an option for your wife.