In reality it proves the opposite. What she describes IS flow. In fact that is exactly what flow is. Flow is a mental state of focus. It doesn't claim ease, it doesn't mean mindless. Its the opposite of those things. Flow requires great effort and energy. She wasn't thinking about groceries, or what she was going to do later that night. She was in the moment. Aware of the music and her body at such an intense level. She was in flow. Flow isn't magic. It doesn't just happen. To get there takes immense practice. To get there takes immense energy. To maintain flow takes both. Yes, to an outsider, to a viewer it may appear as ease, or effortlessness, but flow is not about the observer. Flow is about the performer. The prima ballerina is so practiced that she appears to flow, her movements and beauty seem effortless to the observer. Yet if you were to ask the ballerina she would likely have a million things to say to the contrary, but her thoughts would only be of the dance, because for those moments all of her attention was with her dance. She was in flow. Flow is a state of mind and not a state of appearance. Flow is not about having fun or doing well. Flow is a state of mental focus and awareness.
I am a yoga teacher and I often talk of "ease" with my students. What do I mean by "ease"? I don't need to tell them, they feel it. It comes with much practice. A movement that once seemed impossible, that took immense effort, now comes easier. Its as if your brain and your body have finally figured it out. Does that mean they stop thinking about it? Not at all! It means the exact opposite. Now they begin to think of it at a different level of awareness. Then you work towards the next and the next. It is a constant practice. The author seems to think there should be an end game. A place where the person says, "I've completed all the levels!". I no longer can improve and i no longer need to practice. I'd have to ask in what world has that ever been true of anything? Dance or any pursuit for that matter is always one of improvement and practice. There is no completion. You can stop or continue but you will never complete it.
Some of my students look at me and think some of the things I do are magical. "Wow!", they say. Secretly desiring to be able to do the same things. I tell them that they will with practice. When they do they are so amazed. Still achievement has nothing to do with flow. Instead what is happening is the students are not learning the pose. They are learning to flow. They see the teacher do something and see a body moving and balancing. They attempt it and fail, but each time they try they learn to focus on more and more until they achieve a level of focus and awareness that allows them to complete it. They achieved flow. Sure you'll say but it isn't all flow, its muscle and strength and stamina. Yes all of those things are part of it but none of them are independent from it. As they practice those physical changes will happen. If they do the movements the body will go there. The mind however is a different thing. I've seen the strongest and fittest people not be successful. They are unsuccessful because they don't have the focus and awareness. One is not equal to the other.
So what of flow? Flow exists. Its hard. Very hard. It takes extensive energy and practice to get there. The author was experiencing flow all over the place and simply didn't understand it. She assumed ease meant that it would be easy. In yoga there is a saying that shavasana (corpse pose lying on the floor), is the hardest pose. Yet every beginner will make the joke, hardest?, its the only one I can do! Can you though? You may be able to lie still on the floor but that is not the yoga pose. That is simply the body position. It is the easiest body position in yoga and therefore the hardest mental position. Yoga asks you to find "flow" in your practice. Finding flow in shavasana is very hard. When you are challenged by your strength , flexibility and balance, focusing on the current moment is easy. If you don't you will fall on your face. But finding ease in those difficult poses begins to teach you how to find ease elsewhere. How to flow elsewhere. Ask a yoga teacher who in their class is truly achieving shavasana and who isn't. They will be able to tell you. Yet to you it will just look like a bunch of people lying down. To the observer they all appear to be at ease with the pose. To the trained observer the answer is more clear, but the true answer is only available to the performer. Only they know if they are in flow.