It sounds like a good plan and I hope it works for you.
Have you tried a bottle at night to see how much she is eating? Somewhere in Healthy Habits there is a section on changing either the amount in their bottles or the liquid in them to see if that helps...
I'll tell you though, it sounds an awful lot like my daughter. At 3 months, my baby girl was sleeping 10 hours straight. So, we moved her to her own room. She kept this up for close to a month and then started waking up 2x a night. It was never at the same time though. Sometimes she'd sleep for 2 hours and then 5 more and other times, she'd sleep for 3 and then another 3 hours. Like your DD, my daughter also went down awake for naps and at nighttime, but we still had these night feedings way longer than I thought they were supposed to go on. I tried letting her cio--not feeding her if it hadn't been at least a certain number of hours as well as not feeding her at all. We did this each time for a week, but she held on to the two feedings. In the end, she gave up all nighttime feedings very randomly at 11 and half months. I can't explain why nor can I explain why she woke up in the first place or how she could have been hungry after only 2 hours. We tried bottle feeding at night too for awhile to make sure she wasn't just eating an ounce and then falling back asleep, but she wasn't, so I went back to bfing.
I think CIO is a good option and I wouldn't hesitate to try it with my son should he need it, but I just wanted to share my story since it parallels yours. I wish I'd had more faith that she'd eventually give it up on her own.
Good luck!