As a medical professional I would advise not travelling tonight both for your wife & other passengers/crew safety. Firstly, that is a very long flight in a relatively low humidity & low pressure environment. She will feel awful if not fully recovered.

Secondly, if this is some form of infectious gastroenteritis (& there is something doing the rounds at the moment) then she would be a transmission risk to others until 48 hours after her symptoms subsided. Viral illnesses such as Norovirus are incredibly infectious and there is a high chance anyone in contact with your wife, her seat or any bathroom she had used would suffer the same illness as her over the next 24-48 hours. Clearly this could include a number of crew down route & run the risk of a return flight being cancelled.

In terms of the best route forward I would first speak to your travel insurer, I was hospitalised with Typhoid at the end of my honeymoon in Malaysia and HSBC rebooked me in F 48 hours after my hospital discharge (BA insisted on this window).

Finally, my sympathies to your wife, it is a miserable experience but hopefully it will resolve relatively quickly. If possible I would advise you sleeping in a different room & using a separate bathroom/towels etc. Wash your hands with hot soapy water regularly & definitely prior to eating. Note that alcohol hand gel is ineffective against Norovirus.

Good luck & at least married life can only get better from here!