D.M.
I have to agree with the other two Mommies, this is not a sleep issue...for all intensive purposed babies don't sleep when WE want them too, but when they need to. Your little girl is most likely adapting to a new stage of development, and experiencing growth spurts.
After reading your 'more info', I think you need to pick either a feeding schedule or on demand...both is kind of confusing for little one's. My son was feed on demand, and he slept for good two-three hours chunks of time that allowed me to nap in the morning and catch up on sleep and get stuff done in the afternoon. This was usual for us until he was seven months old and had been on solids for a couple of months, then it was another change. Truthfully, I would advise you to just go with the flow, and let your little one guide as to what SHE needs from YOU right now. Waking her up to feed her so, she doesn't wake you up almost seems counterproductive to me...let her needs be your guide to feeding and sleep.
It was tough for me when my son was that little because I worried if he was getting enough to eat, and enough sleep. But, he was the best judge of what he needed from me and just had to listen and watch the signs. Once he was ready to transition to longer sleep periods that was a whole other experience, but you just have to be prepared for constant changes to the 'routine' and forget about all the timelines or what other peoples kids are doing.
Good Luck.