I did it when DS was 16 months old. He was terrible before then, had to be rocked off to sleep then sneaked into cot - it was taking hours on a night, sometimes up to 3 hours!
He was a real screamer and I was convinced it would never work with him, I tried it when he was younger (just once) and he cried so hard his nose bled.
BUT when he was 16 months I tried again. The first night it took about a hour, second night 30 minutes and by the end of the week (i.e. 7 nights) he was going down on his own with no tears.
Once that was established, I did it at nap time too and that worked within 4 days.
I think it will help you, if it works with Eimear, as you will have some time to yourself at SET times so you know what you are doing.
I don't think it would have worked earlier with my ds, but I'm so glad I did it now.
Big hugs to you, I really hope it works for you, I know how hard it is listening to them cry, but as long as you are checking on her regularly (as your post says you are), she's not going to come to any harm in her cot! How old is she? Keep us posted.
xxx