Does she drink milk? If so the extra calories will fill her up. Juice/squash will ruin appetite because of the sugar. How many snacks does she have?
My 2 year old eats well at breakfast and lunch but pick at dinner. I think she's just not hungry enough! We kind of made up the idea of eating 3 times a day with snacks but in reality kids only eat as much as they need.
Also does she get enough physical outdoor play? There's so many factors!
We eat at 4.30pm because I don't give an afternoon snack and they're hungry, also eating too late means my toddler is too tired to eat properly. Have a look at your routine?
My 'fussy' toddler (really just picky)
Prefers foods which aren't slushy (with the exception of baked beans and bolognaise) so she won't bother with mash or pasta dishes etc. she prefers things like fishfingers and chicken nuggets but I make my own nuggets (roll chicken breast chunks in beaten egg and then flour) and I do homemade wedges instead of mash.
Another tip is to have lots of pots and dishes they can serve themselves. We do jacket potatoes and put various salads, cheese, beans, coleslaw etc on the table. I know she won't eat much potato but fills up on the bits, she also likes olives, beetroot, sweet corn etc. this can also be fun with noodles and vegetables in little bowls. It's amazing what they tuck into when it's self choosing. Sometimes I just put bread and butter, cheese cubes and sticks of cucumber on the table if we're having a 'mushy' meal like cottage pie.
HTH and remember toddlers are notorious for being picky, it is just a phase as long a you handle it right and don't put any pressure on, eat together as a family at the table and really tuck into yours. It will happen eventually.