Sleep issue

Hi, does anyone's preteen struggle going to sleep?

My daughter is nearly 12 and has always had a good bedtime routine but tells me she struggles to go to sleep.  She is normally in bed at 9pm, 10 at the latest but she will often say she isn't tired and tells me she struggles to go to sleep for another hour or two.

I think 9-10 is a good bedtime.  She does seem to function okay but I do notice some days she yawns quite a bit.

Looking back when she was much younger, she would never seem tired or fall asleep early.  She also tells me that nothing is playing on her mind to worry her which would keep her awake. 

Does anyone have any suggestions or is dealing with similar sleep issues please.  

Thanks