I think you may be able to try to introduce half a meal (eg. if normally your baby eats 4 oz, then give her 2 oz) in between 2 meals towards the evening time (some time between 4 to 8pm). Then you can shift your subsequent meal for another 2 hours.
I tried the same with my daughter around 4 weeks ago. It did not work for 2 nights, as she was still waking up out of habit at around 4am. But on the 3rd night, she slept through the night ! Last meal at 11:45pm and then I will feed her again at 7am.
So keep trying, if it doesn't work, be persistent and try it for a few more nights. Add oil!