Sometimes LOs are just too tired for the DF. They just want to go back to sleep. If she's giving you signs that she's not hungry and can last until morning, I would let it be and count yourself lucky. If she's waking up a few hours in the night for a feed and you want to help her last until morning, you might need to give her slightly less ozs at the 5 & 7 feeds, so that she's hungrier at the DF and will hopefully take more.
Some babies never take to the DF or show signs of dropping it early. My DD never drank a lot at the DF, maybe 4ozs at most and then around 4-5 months started refusing it altogether and lasting until morning without it. Just go with her cues.
Good luck!
