Given the UK government guidelines issued to British airlines regarding the requirements to prepackage and offer sealed food wherever possible, I think this may be having the negative effect on the output to a greater degree. That said, Virgin Atlantic can offer hot food in all cabins.... all be it a reduced offering.
Information relating to an existing thread regarding revised catering can be found
here
A revised service of on board catering including alcohol service and hot food in First is due to go live this week so perhaps it was just unfortunate that your wife travelled when she did. That said, the revised offering is essentially still a sandwich box and a hot Economy style meal..... Far from a First experience so don't get your hopes up too much.