FIRST I WANT TO SAY THAT YOU ARE DOING A TERRIFIC JOB!
My kids are now 15 & 19, but my adage when they were you was "LOVE THEM PROFUSELY, teach them right from wrong, & encourage them to become that which they were created to be & they will have nothing to rebel against" (So far so good)
However, it can be exhausting to be constantly investing!
Perhaps this will work with her. Use a timer, set it for 5 minutes, show it to her, then sit down to color with her. Before she knows it, the timer will go off. Perhaps repeat this a few times, so she can learn that 5 minutes isn't very long. Then explain that you need 5 minutes of undivided attention to make a phone call, finish the recipe, or what ever you need to do. As she gains a concept of time, you can lengthen it, to say 8 min, then 10 min. I would tell my kids, I am not available for the next 20, (whatever) and unless some crisis has occurred, or someone is bleeding, DO NOT INTERRUPT ME. Seems to me that as soon as I closed the door to use the toilet by myself, or tried to take a short nap, that someone needed something.
It is developmental, as another gal wrote. When a child is born, they do not know the difference of where "I stop & you start." Their whole universe revolves around them. It is a slow process as they begin to differentiate between her and you.
One of my favorite books, because it covered child development so well was DR SEARS: GUIDE TO CHRISTIAN PARENTING. He is a psychologist & a pediatrician. Even if you are not a Christian, the research & experience in this book about child rearing is amazing.
One of the premises that he teaches: A need met goes away, a need that goes unmet will go underground. Children have different stages that they go through. (we all know that) and that one builds upon the next. Everything we do with them is laying a foundation for the next step. When her need for connection is met, then she will begin to move towards autonomy. If a child needs attention, & they do not get it in positive ways, they will start misbehaving, because any attention is better than no attention. No worries, no parent is perfect & no child is perfect. Just separate out which is testing or defiance, & when it's a basic human need at the root. It sounds like you are doing a terrific job of meeting her needs, and when she is satiated, (all children have differing satiation points) she will move on.
If you can bear one more thought....
If you have a project that will take a couple of hours, invite a friend over for her to play with.
God Bless you,
A.