Help!

Ok, so here's the deal.  I have this little stinker of a 2 year old who's never really had good sleeping habits.  At a pretty young age she stopped taking regular(and scheduled) naps altogether.  For probably like 10 months we've been trying to find the balance between her taking naps because she sometimes needs it and her still going to bed at a decent time if she does and it just hasn't worked. 

Some days Arya plays really hard, she is a very high energy toddler and so when it comes to sleeping she never seems ready to settle down.  But there are days when it hits about 4 in the afternoon she just cannot stay awake. We often try stimulating her to keep her awake and offer her things, like going outside, that we know she loves to do to keep her awake.  That doesn't really work though when she's been playing outside and she makes her way inside to fall asleep.  Yesterday we were busy all day and so I knew Arya would be exhausted and sure enough I am nursing Bracken and I take my feet off the ottoman and set them on the ground only to find that I have a 2 year old laying at my feet, completely out of it, who didn't even budge when I almost stepped on her.  No amount of persuasion would wake her up at that point.  I couldn't worry about it more though because I was taking Audree out on a mommy daughter date. 

I think she only napped for about an hour and a half but for some reason any amount of nap during the day makes it so she wont go to sleep at night.  And I'm not talking like she stays up til 11, I'm talking like 2 in the morning.  We talked to her pediatrician and his only advice was to make sure she starts her nap before 2 or don't let her nap at all.  Way easier said then done!  She is not even remotely tired at that time of day and she hasn't been for like a year now.  But I swear around 4 or 5 some days she gets hit with extreme tired and then is out before any of us realize it.  There have even been times where we've been playing at a friends house and we find, that instead of playing, Arya has made her way into the crib and conked out. 

Some of you may think that we just need to try harder to hold her off for 2 or 3 hours once she wants to nap but putting her to bed before 8 is not an option or she will also treat it like a nap and wake up and be ready to play for another large chunk of time and again one of us has to stay up with her til 2 or 3 in the morning.  This is not ok!!  But nothing we've tried has worked. 

Arya is a very independent and very strong willed girl.  It is not in my parenting belief or style to try and "break" her will.  I think trying to break her strong will would not be beneficial to her future self as having a strong will could be very beneficial to her.  So I am looking for help of the gentler persuasion.  I don't have much hope of these random late naps ending any time soon.  We've been waiting for nearly a year for her to grow out of these habits but it hasn't happened yet.  So I was hoping that all my friends who are big on the essential oils could give me some suggestions.  I was hoping there would be a good solution for those days where she does take naps and doesn't settle down until way late at night.  I'm not talking something that is just for calming though.  We've tried some things and calm Arya still isn't tired enough to go to sleep.  I need something that will help her be calm AND go to sleep.  I'm not, at this point, really interested in knowing all remedies for everything and spending hundreds of dollars.  I just need a solution for this and don't want to go back to the doctor just for a solution that I already know isn't working. 

Help!