Wtf has happened to sleep

[Fluffballs]

Anyone got any idea how I can get 11mo to sleep?
She co slept until around 8 months, transitioned into her own cot at 9 months and went into her own room surprisingly easily at 10 months.
Over the last couple of weeks she's been waking up more and more frequently, then last night started screaming from 10pm until 12. Then decided it was play time until 2am.
Tonight she wont entertain the idea of, calmdown/bed time at all and has been screaming for the last hour already and it's only 6pm.
I've tried everything, she won't even calm down on the breast. Not ill, don't think it's teeth.

I'm absolutely not asking how, or expecting her to sleep through the night, just how to go to sleep. And why she's had such a dramatic turn.

What time do you normally put her to bed? Sounds like she goes quite early.
What are naps like?

She normal goes anytime between 5-7, depending on when she's looking tired. I've thought about pushing it back but she's yawning and grumpy from about 4!
Naps are great, one at 10am, one at 1pm. Roughly an hour each

Sounds like a sleep regression to me, maybe the 12 month one a bit early. Stay strong!

Thank you, hopefully it doesn't last too long then