L.T.
I don't see her weight as being an issue. All babies are different. My older son can outeat me and he is in the 10% weight and 75% height--it's how he is made.
Is your daughter still nursing? breastmilk has tons of fat. Also, if you need more fat, look into avocados--loaded with healthy fat. You can also add ground flaxseed to her food (more healthy fat). Olives have lots of fat too!
If you are doing goat products, try goat butter (whole foods sells a really yummy one).
Are you doing meat? If so, try bacon--the KING of fat (and odds are she'll just love it).
Head growth is not related to food--if your ped. is concerened about head growth, you may want to talk to a specialist to make sure all is well but if her head circ is growing, odds are she is just fine!
L.