Hi C.! I was in the SAMEEEE situation a couple of months ago and I knew it my fault as well. Bella (almost a year now)would get up b/w 2-3 times in the mid of the night and it all started because she had a cold. Her cold went away, but she still kept getting up.
One night I accidentally (really, it was accidentally) turned the volume down on the monitor and fell back to sleep, but not long at all. I heard her crying in the monitor and was ready to go downstairs to do my mid of the night feeding as I had been for about two months at that time. However, this time I fell back to sleep. When I realized what I did, I made my way downstairs and she stopped crying when I reached the bottom of the stairs. I was shocked!!! So, I slept on the futon in her room and waited for the next wake up call about 230am. That came and I let her cry, but it was only for a a few mins or so. She cried and it wasn't like a hystercial cry or anything. To my surprise, she fell back asleep!!! I was in shock once again! This hasn't happened in months, so I was so happy! Did I really break her of the habit I thought?
Well, for the next five nights, Bella would cry a little mid morning and fall back asleep on her own. I would not go in to soothe her or anything. By the sixth day I believe, she was cured! No more mid of the night feedings and I have been getting sleep!
I was SOOO sleep deprived before this and it was getting to the point where I knew I had to do something. I'm not sure if I could have "let her cry it out" if I didn't accidentally turn the monitor down. I'm not sure what I would have done honestly.
One thing I will suggest, is that you try to soothe her back to sleep or rock/walk her instead of nursing her. If you decide to let her cry it out, go in every now and then and pat her on the back but don't pick her up unless she is livid. Next time you want to go in and soothe her, wait a few mins longer than last time and keep doing this until she falls asleep. My sister tried this and it worked, but it was a long process.
I do feel for you and hope that whatever you decide will work. It's worth your sleep to get her back on track =-)
-P.