Honestly I worked for over ten years in various capacities in a school district. Rarely if ever did I come across a child that was really ADD....most just didn't know how to listen. Given the right environment with consequences they cared about, they would often behave well.
Do you make her listen? What do you do when she won't follow instructions? Do you insist that she follow your instructions or do you beg, plead and try to bribe her into listening to you?
If you have insisted that she respond when you call her name, by getting in front of her at her level and holding her little face gently to stare you in the eyes when talking to her.....and you physically but gently make her pick up her toys when you ask her too....and you physically, but gently make her sit in her seat....
then I would say that she might have a problem. And food does have some impact on how children behave so does lack of sleep for that matter, but ultimately they have to learn to behave regardless of how they feel....or they grow up to be whiney, complaining, wimpy adults that can't deal with the smallest amount of disappointment or stress.
Next time you call her and she ignores you, immediately get in front of her, squat down to her level, gently grab her little face and make her look at you....tell her "mommy is talking to you, you need to listen to me". If she tries to pull away from you, insist that she look at you. Insist that she does what you have asked her to do even if it means gently grabbing her by the arms and taking her to the task and making her perform the task.
Does she look at you when you are playing? Does she make eye contact when she wants something? Then she can look at you when you call her name and she can do what you have asked her to do.
My girls were picking up their toys at that age...I would direct them one toy at a time, but they did it. I would say Avianna pick up the baby doll and put it in the toy box. She would pick that one up and then I would direct her to the next. Wasn't long before she could do it without my help.
And if they ever ignored me, I made it my business to get their attention immediately. I still do and they are six and four. I NEVER let them ignore me. I might call them once or twice more if I think there is a chance they don't hear me, but if the continue to ignore me, they will suffer the consequences.
All children will try it....you just have to insist that they stop.
PS And please don't think she's too young to listen. My kids and the kids I watch learn very quickly to listen or I will help. She listens if you tell her you have a treat right? She comes running if you tell her you are going to do something fun right? She can listen when you call her name or ask her to do something simple. At that age keep instructions simple, but please insist that she follow your instructions. You will be a proud parent of a well-behaved child before you know it, if you insist now.