I know how hard it is not to worry, but really there is no need. Babies/toddlers are really neat in that they really do know what they need to survive. She will not starve herself and will eat when she's hungry :)
My oldest son is 2.5 yrs and has always been below the 5th percentile in weight. Finally at his 2 yr check up he made it to the 20th percentile. And mind you he eats like a champ. Even today he still only weighs 25 lbs. As I've told many other moms they are each on their own curve. As long as she's on her "curve" there's nothing to be concerned about. That's the advice I got from my ped., and I'm sure that's why yours is saying there's nothing to worry about. The first couple of visits it was hard for me not to worry, but I saw how I had a very healthy, active, energetic little boy. There really wasn''t a reason to worry.
Just offer healthy snacks, and let it be at that. One thing you don't want to do is 'control' what they eat, leads to bigger problems down the road. As a toddler as you've noticed they are busy exploring and really don't have the patience to sit and eat a whole meal. I always have to remind myself they only need to eat a meal the size of the fist (which really isn't that much).From day to day their needs will be different as well. Some days they may eat dinner the next day they may not. As soon as I stopped make a big deal out of what my son ate, I noticed he was more willing to eat what I offered him.
Best wishes mama you're doing great..Next thing you'll know you'll be just like me and another child that is the complete opposite..and you'll worry your over feeding him...My 10 month old and my 2.5 yr old weigh the same, where the same clothes and everything..Every baby is different :)