My other half just got off a Royal Brunei flight from Brunei to Auckland in a completely exhausted state.
The flight crew called for a doctor and she spent the entire flight tending to a sick passenger. They told her that if it hadn't been for her help they would've had to turn the plane around and go back to Brunei.

Should she ask for some type of reward?

A little bit sucky was that they moved the sick passenger to business class and she spent the flight schlepping from econ to business to check on the passenger every hour, after giving the passenger an initial 1/2 hour examination.
Also , they asked her to speak to paramedics upon arrival in auckland and said they'd help her make her connection on time. However, once she got to auckland they just left her to it! Luckily she made the connection anyway.

She normally flies from Christchurch but was flying from Auckland in a unusual circumstance.

She's used to this type of thing being a doc, but seems to me like she should get some type of reward? What should she request? some cash back on the flight would be the most useful since Royal Brunei don't fly from our home airport.

btw, she wasn't impressed with the medical kit on board. Said it badly needed updating!

If she hadn't been so tired I think she would've been more assertive on board but had only stopped over for the day in Brunei so was already tired.