Good luck with a comp upgrade on an award ticket; while the rules do state that Elite members with the Mileage Plus Visa Card are eligible for these upgrades, they are incredibly difficult to get. And, your friend (unless and elite member) is technically not eligible for this benefit.
These upgrades are prioritized on the lowest level (day of, once all other elite upgrades are processed), but Hawaii flights might be easier since they aren't as elite heavy.