If you can swing it, Singapore Airlines First Class features insanely wide seats (something like 35" wide on the 77W); I felt a bit like a kid sitting in an adult seat due to the ludicrous width. Cathay First is also a pretty wide seat.
The Cathay Business Class seats may be problematic for your friend. The width may be manageable with the armrest down, but getting the tray table lowered may be a problem. The table tends to sit fairly close to one's lap, so it could be an issue.
I haven't flown SQ Business Class, so I can't speak to it directly. But they do appear to have relatively wide seats across their fleet.