First - 5:30-6 pm sounds like a REALLY EARLY bedtime, which is going to translate to a REALLY early wake-up time. See if you can shift her back an hour and consolidate her day-time naps, so you get some decent rest too! I know, people always say that their kids go to bed at 7 pm, but our son always went to bed about 9-9:30 pm, slept until 7am, and has a great long nap in the afternoon. Every kid is different though.
Really, you NEED to get Richard Ferber's book, "Solve your child's sleep problems". This book changed our lives! It is really informative - much more than just the 2 sentence description of his method of getting your child to fall asleep on her own. He talks about natural sleep rhythms - that your child will wake up every few hours, as part of her sleep cycle, but the key is to get her to just roll back over and sleep again. You're actually more disruptive to her sleep by picking her up & nursing, than to wait, see if she goes back to sleep. From what you described, you're not really using a CIO method at all. Ferber is great, but the key things are: get your child to soothe herself back to sleep, DON'T pick her up, and work with her natural rhythms.
Also, our pediatrician recommended that we wait 20 minutes during a wake up to see if our son would go back to sleep. Sure enough - he did. And after he did that a few times, he started sleeping through the night.
Having said that, this transition is going to be REALLY HARD for you guys if you're all in the same room. If your daughter sees you, she's going to be really mad (i.e. crying) if you don't pick her up. Can you move her to an office room, or have you start sleeping in the living room? I know it's not ideal, but the situation you describe where no one is getting any sleep is horrible, and not sustainable.
I hope you get some rest soon!