You're pretty close to flight date so I think you should be ok:
- If there are still seats available, they may open up D class a couple days prior
- Good chance you can upgrade at check-in (and since she's already upgraded, you can share her car)

Do note that 19 unassigned seats on the seat map does not mean actual seat availability. EF does show at least" F4/J7/Y9 (max for each bucket).

Your chances are good!

Good luck on the question! (ask her on the plane, the crew will love it)