Up until a week ago she was fine. We had a great routine - milk downstairs, then she'd get her blanket and dummy and we'd go upstairs, 2 stories in bed, a song and tuck her in. She settled herself with the door shut and light off, no problem. she did this from before she was a year old.
BUT.. This week I seem to have a different DD
As soon as bed is mentioned the tantrum starts. I calm her down, coax her upstairs and she's fine with her story and song, but starts wailing again when I leave. I've tried putting her back and ignoring her, laying with her until calm, going up earlier; nothing is working. I have 2 other dc so can't really do CIO - we tried once but it meant ds was kept awake then he was up and down for an hour 
I thought I'd cracked it tonight - she wanted to sleep in ds bed, got straight in and didn't move. I stayed until she was asleep (only 10 mins) but she woke at 11.30 and has been awake since, even when I got into bed with her.
What can I do?? 10 week old has been sleeping through for a fortnight so we'd just got used to mostly u disturbed nights too!