Whether she can or wants to eat or not will depend on how her birth goes, whether she has any interventions, and what her hospital's policy is. Some encourage birthing mothers to eat, others discourage it, some say clear fluids only. Sometimes women vomit in labour and don't want to eat. Sometimes they get up to the postnatal ward and they've just missed a meal and they're absolutely starving and no one brings them anything to eat for absolutely ages.
So I would bring things like: water, clear juice drinks, cereal bars, dried fruit, nuts, maybe some boiled sweets, chocolate raisins, that sort of thing (depending on what she likes, obviously). Chewing gum in case she can't eat but wants to taste something. And for after the baby is born, some emergency rations in case she is starving and can't get a proper meal. Some sort of sandwich with a filling that will survive not being refrigerated for a while. Maybe some pepperonis or something like that.
And I particularly recommend oaty things. Oats are recommended if you are breastfeeding anyway (not sure how reliable the science is behind this) but even if you're not, they're a great energy boost when you're starving during night feeds, and it doesn't feel too much like eating junk food in the middle of the night. A friend of mine gave me a packet of chocolate covered Hobnob flapjacks, which were exactly what I needed at 3am after giving birth. Failing that, any kind of flapjacks, oatmeal and raisin cookies or just a packet of Hobnobs would be great. You can stuff them down in the early hours and kid yourself that it's just like having a bowl of porridge really.
It's not wise to eat particularly strong tasting food immediately before giving birth in case you're sick during labour. Things like curry, fish etc taste really awful coming back up again. I had tinned mackerel mixed with rice as my last meal before going to the hospital, thinking it would give me lots of slow burn energy. All it did was make my sick taste particularly foul. 0/10 would not recommend. If I ever had another baby I'd eat something very bland beforehand, like pasta with butter.