If you don't feel the DF is working for you then it's ok not to do it. You can just continue with her waking when she's hungry.
I would say, she is very young to expect a super long stretch at night. 5hrs is considered sleeping through and you are getting this already. I wouldn't expect 7hrs just because she's done it before simply because there are so many growth spurts when they are so young and with a growth spurt she's going to feel hungry sooner, maybe even need 2 night feeds rather than 1 and that would be totally normal. The DF really is something which helps parents so that the LOs long sleep comes at the parent's bed time, but there is nothing wrong with you going to bed early when you need an extra sleep and making the most of that long stretch from 8pm to 1/3am.
FWIW my LO never too a DF, but would eat at that time, awake. In the early days it probably meant he was awake an hour because of the length of time to eat, change a nappy and put him back down (even though he went down pretty easy and straight back to sleep) but as he got older he was awake for a bit less time and the putting down was even easier. Just nappy, feed, back in bed.