G.B.
Trying to make someone's body change from years of the same schedule is really not good for them. I assume the competition will NOT start at 6am but that you are traveling to it.
She can get up, get ready, get in the car, go back to sleep if she's able, etc...I think being well rested means not going out the day before and going on a 10 mile hike, not riding a bike in a BMX race, not jumping on the trampoline for 3 hours right before bedtime.
It won't hurt to have her lay down earlier but chances are she will lay there and fret and work herself up into a mess. I do believe that giving her something to make her more able to sleep may have side effects the next day that will change the outcome of the competition. Nothing like going into a competition while hung over with drugs in your system.
Let her watch a movie, TV, or read a book, do something quiet and restful so her body is resting but her mind is not being taxed. She will be fine for her competition.
I hope she does well.