She's already going to bed around 8:30, but even on nights where she's stayed up late she still seems to do this at the same time!
My LO is doing something similar atm, he doesn't want to be put in his cot or even Co sleep from 4/5am so I have to sit up and hold him whilst he sleeps and he also sleeps around 8/8:30pm.
My older one used to do that at that age. I know how it feels! Have you tried putting your baby down while she's in a deeper sleep, so after 20 mins? Sometimes it was working for me so worth a try if you haven't yet.
@Bahar I tried that this morning and it didn't work but I'll keep trying/waiting longer for her to be deeper asleep
What time are you putting her down in the evening? Could you delay bedtime by 30 mins ?