I think what the problem is, and you said it, "and after about a week of getting up in the middle of the night to nurse her,my exhaustion takes over and I decide to let her cry again." It is you, not her. You are setting the pattern and the bad habits, not her. She is following your lead. It is normal for a baby to wake up multiple times in a night and it is exhausting for every mother, we have to deal with it.
You are not being consistent so how can you expect her to be? You need to either continue to nurse her or not, it is not fair to your daughter to give her mixed signals. Either way the cry it out method did not work for her so you need to find another solution. If you are going to nurse and want to stop slowly shorten the time you are feeding her until she is no longer nursing. Offer a pacifier for comfort. There are a couple of good books, like Healthy baby Healthy sleep habits, or something like that. Either way, it is your bad habits that need work on, not hers. Babies thrive on routine and what you are offering is anything but routine. Hang in there she will outgrow it, but until then, plan to be tired. Good luck
Also this is so normal, but your case is extreme because you are not consistent.