Maybe she's transitioning out of feeding to sleep? DS was like that too when it stopped working all the time. It's hard, because it takes a lot of effort to get something else working in its place when they don't want to sleep.

I would keep feeding to sleep during the night for now, if that works best, but maybe start doing something else at bed time. That *might* be more successful and she *might* then get the hang of other things during the night. What time is dinner? We ended up doing dinner at 4pm to get him in bed by 7 (because it took 1-2 hours for him to unwind and relax enough to sleep).

I gave up on the cot at around 7-8 months and slept him on a mattress on the floor of his room (I slept there too most of the time). When feeding to sleep wouldn't work any more I started lying down with him, cuddling. Sometimes it worked, sometimes he just crawled all over me. He's a fan of singing too. It's a really hard time, because they soooo need to sleep, but just don't want to. And you end up spending a lot more time getting them to sleep than they actually sleep! Not worth it

Maybe try a teethign necklace in case of teeth...? Can't hurt anyway if you don't already have one.

DS was the same with day sleeps till 14-15 months I think, when he finally started sleeping more than an hour.