D.M.
I never found a diaper bag that carried everything I needed...so, for days out to places like the zoo, park or even mall I'd use my Adidas Backpack that I used to use for hiking, as it was insulated and had bottle holders on the side. I carried what I needed...diapers, wipers, one bottle with milk/juice, snack, change of clothes and toy/book. Otherwise, if it's short trip to the store or meal out, I simply carry what I need in a tote type bag (purse) that has great pockets inside and was actually supposed to be a beach bag!
In my car, to this day, I keep an emergency change of clothes, diapers, wipes and a cooler that I use for longer trips away from home...zoo, park, beach, etc.
Not sure how old your little girl is, but I know when my son was born until recently (he's 2) I used to carry everything including the kitchen sink and at some point I realized I could start leaving things at home...I love the suggestions of searching for a diaper bag backpack...they are great!