I think it's really important to start the day when you normally wake up for the day, or at least when your baby wakes up. Say for example baby wakes me around 6:30am, that is when I will start the day. So we feed at 6:30, and then I shoot for feeding again in 3-4 hrs after the first nap. If baby doesn't wake for the day until 8am, then that is when the day "starts". 7am is just a random time, you need to make it work for you.
Yes, babies may still need one nightfeed around 5-7 months, some even have one night feed until 12 months! Even if you df at 10pm, she still may not go through until 7am-ish. They wake so often at 5 months old for other reasons and think feeding is a great way to get back to sleep, so it is always hard to determine true hunger. My ds fed once per night until much older than your baby.
For more sleep related issues, you may want to post in our sleep forums. We breastfeeding moms can answer questions about nursing and give support any time you need it!