Speaking strictly about the alleged "ginger afro" conversation, here's what Bower said in Revenge (p 626 of the epub edition): In one version, Camilla remarked, ‘Wouldn’t it be funny if your child had ginger Afro hair?’ Harry laughed. Subsequently, Meghan’s reaction to that conversation turned Harry’s amusement into fury. (The source for this is “Finding Freedom p.124/5”).
There's a tendency throughout the book for Bower to use quotes around statements that he has not footnoted (for example, there are numerous unsourced direct quotes from Meghan that are couched in British English which most Americans would consider grammatically incorrect). Since this quote ‘Wouldn’t it be funny if your child had ginger Afro hair?’ is sourced, I'd encourage people to go to the source here; I don't have access to it.
However: if the claim is that Camilla's comment is racist in context, why did Harry laugh at it? He later realised, in conversation with Meghan, why it was racist - but did Camilla also hear those reasons, and the hurt it caused, and double down and stand behind the comment? Believe me, I have every sympathy with Meghan not wanting to have to de facto do the work of telling white people about racism - but once she had told Harry, why could HE not have told Camilla or whoever? Perhaps he did and I'm missing it, but so did Bower.
I do agree that overall the Bower book comes across as racist (and xenophobic). He seems to be desperate to prove that Meghan was exaggerating the impact of anti-black racism in the USA, because he was able to find sources that said that racism was not a significant factor in certain specific situations. Meghan recounts a specific racist incident at school, but a teacher at the school that Bower corresponded with decades later said she didn't feel there was racism, so Meghan's integrity should be questioned. A producer who hired Meghan said he didn't know she was mixed race, so that negates her perceptions that she struggled as a mixed-race actress in Hollywood. Thomas Merkel said Meghan never confided in him about feeling marginalised as a black or mixed-raced person at Northwestern, so she can't have experienced racism there. And on and on and on (I'm only at the part where Meghan and Harry are engaged - and no, I did not buy the book!)
The fact is, Meghan had and has every right and reason to come to a realisation over time about how much anti-black racism - including prejudice against mixed marriages, etc. - impacted her at various stages of her life, and to decide when to speak out about it knowing that the backlash would come. And as Bower gets race in the USA so spectacularly wrong, it becomes hard to take his word for anything.