In terms of freedom of speech, which I support in every form: complain any way you want.
In terms of smart career advice and behaving like a professional: DON'T.
In the many comments about the Magic Under Glass cover, a few people have wondered about the author's relative quiet. It seems there are two very different questions, though:
Some people seem to be asking "Why wasn't the author the very first to object publicly to the cover?"
When you, as an author, form a professional business relationship with a publisher (ie, contracts, signatures, money changing hands), the publisher expects you to act professionally. What that means is that in most cases, you should take a 'no comment' approach to the publisher's mistakes, in the same way that the publisher will take a 'no comment' approach to your mistakes, if you make any.
If a newspaper article runs about the time you accidentally showed up at your job clothed only in tequila, your publisher will not be happy. But to the public, its response will be 'no comment'. You are its business partner, and short of canceling your contract, that's not going to change. So your publisher realizes that if it became one of the people publicly objecting to your behavior, that would not help the situation. At all.
And the same goes in reverse. I would say that the only time it would be smart to publicly distance yourself from your publisher is when/if it has done something that will cause continuing public outrage and bad feeling even after it makes an attempt to mitigate its mistake. You may have noticed that much of the outrage and consternation about the cover is dying down now that Bloomsbury has capitulated. This was not one of those times.
So while I, like you, am curious what the author's personal feelings about all this are, I don't feel she should have felt any pressure to share them with the world.
If your publisher does something so outrageously offensive or stupid that other publishers (the other publishers you would be going to if your current publisher relationship soured) want to distance themselves from it publicly, then THAT is your invitation to excoriate your publisher on your blog and twitter and to burn them in effigy on your front lawn. Not before.
And you should take comfort in knowing that unless you decide to start habitually showing up for school visits clothed only in tequila, your publisher will let you deal with your mistakes your way.
But some seem to be asking, "If the author has no problem with her cover (if in fact that's so, and she's not just being discrete), what gives other people the right to find it objectionable / racist?"
Excuse me? The author is not the arbiter of what cover matches her text when there is an obvious contradiction. No one, absolutely no one, would describe the model on the cover as "dark-skinned", which is how the author described her main character.
One of the problems we have with racism today is that a fair number of people think that racism can only be deliberate. As in, it doesn't matter if something you say or do is racist. If you didn't mean it to be racist, then it's not.
For the record, and I hope we're all really listening: THAT IS INCORRECT.
And also for the record: those of us who objected to the cover were not objecting on the author's behalf. We were objecting on the readers' behalf. And especially on the minority readers' behalf, because some of us understand how excruciating and demoralizing it is to children to be made to feel that they are the wrong color. This is a question completely outside of the author's participation or non-participation. No matter who approved or disapproved that cover, no matter what was meant or not meant, that cover on this book was wrong.