How can you 'force' more sleep on a always grumpy/angry 3.10 year old?!

[EggsOvaryZee]

As it says. DD has never done more than 10 hours. I think she just needs less than Ds whjo does 12, but I may have to accept that her appalling behaviour must have something to do with her lack of sleep...?!

Someone said take everything out of her room but I don't agree with this, and she won't understand.

Normally we leave her room at 8pm but she is still drawing or looking at books, or listening to a tape (quietly) til sometimes gone 9pm!!! She then occassionally has to be woken in the morning around 7am. But then sometimes, she can be awake herself from 6am, even if shes had the same bedtime IYSWIM.

She is ALWAYS grumpy/angry when she wakes.

Any ideas?

It's very disturbing for her 5 yr old brother who often can't sleep with her still awake since neither of them wants their door shut and we're in the smallest excuse for a 3 bed you coud imagine!

I'd say just a more strict routine. My youngest two are now 7 and 9 and still go to bed at 7pm. They just need lots of sleep. If they go to bed late they still wake up at the same time, they're just more grumpy the following day!
I'd talk to her about the new routine, explain exactly what will happen and what you expect. No more drawing/music etc after story and lights out. If she does then I'm afraid I would take these items away initially. Not as a punishment, just to keep temptation out of her reach.
Mind, her behaviour might not be lack of sleep, you could just have a more wilful, different personality on your hands to what you're used to

Might she nap if you took her for a long drive in the day while ds is at school?