Gradual Withdrawl is another very calm option for sleep training and we have used it very effectively at many stages.
The theory behind it is that you slowly change one thing to make her sleep less dependent on you, but changing it only as much as she can handle and still be comfortable. It is the only thing that DS and I are both comfortable with and I have used it at various ages with lots of success. It does "prolong" things, which you are not happy about I realise, but if WIWO is upsetting her, then I see that prolonging things as well.
So right now if you are rocking her to sleep, using GW what you would do is start putting her down earlier. So putting her down when she is almost asleep, and probably for the first while you will have to stay next to her and either keep a hand on her or rub her head, or something else she is comfortable with. If she is upset that you have put her down and it makes her wake, continue to try to settle her in her bed.
Once she is happy being put down semi-awake, (say 3-5 days) then start putting her down MORE awake than she was. Again, you may have to stay with her for a while and comfort her in her cot. In the early days of breaking rocking (which we go through every time DS is ill or teething, so I've been through this process a LOT!) I end up having to stay with DS until he is sound asleep.
You will continue putting her down more and more awake, as she is more and more comfortable with it, until you can put her in her cot without rocking her at all. I find that when we get to this point, DS will still need me in the room, and sometimes after a while of thrashing around trying to settle himself, he wants a bit of a cuddle and climbs up for it. I do give it to him, and usually after 30-40 seconds he climbs back out of my arms and into his cot. After a while, when he's able to put himself to sleep in his cot without rocking, I am able to put him in his cot but sit down at the foot of his bed near the door - if he needs me I can let him know I am there, but don't always have to go to him. Once he gets used to that (say 3-5 days again) I am back to being able to put him in his cot, kiss good night and walk out. If he gets upset after a few minutes of trying to get to sleep, I go in, over to his cot and get him comfy again, kiss, rub his head, and go out again.
It may take a bit longer -- 3 or 4 weeks I think has been our longest at this age -- but we are both much more comfortable with it. When I do get to the point where I can be doing WIWO I don't leave him to the point of tears, as soon as he is shouting for me with a bit of emotion in his voice (annoyed that he can't get to sleep or mad that I have left) I go in to him - so before the tears start. But with the GW, it's very gentle, and if she has been ill, she may just need that extra comfort.