And the fairies here are other enough that I cannot read any current fairy YA these days, all of which seem to have fairies who act mostly like immature adolescents.

That's very true, and a reason why I was awed by these fairies! Also, the book's take on young Elizabeth is absolutely plausible and good. Re: Mary, though, while certainly near the end of her life her relationship with Elizabeth was terrible, for most of their lives it was more complicated than that (and even then, note that dying Mary still made Elizabeth, not one of the remaining Grey sisters or for that matter Catholic (!) Cousin Mary Queen of Scots her successor). And Mary always struck me as a truly tragic character. Right up to her coronation, she fulfills all the fairy tale tropes: after an early childhood with loving parents, her life goes to hell as her mother gets bullied and abused non stop by her father and she herself gets bullied and abused to side with her father against her mother and proclaim her own illegitimacy. From Mary's pov, Anne Boleyn even is the ideal cast for the evil stepmother, as Anne does behave badly towards Mary - as Anne herself acknowledged; one of the things she did before her death was to ask one of the ladies attending her to go to Mary and tell her Anne was sorry -, insisting Mary was to serve her own daughter in her daughter's household. Mary doesn't even get to be with her beloved mother when Catherine dies. And then Anne is executed and there's worse to come, because until this point, Mary could reconcile the beloved father of her early childhood with the one being cruel to her by blaming it all on Anne. But now Anne is dead, Henry is on to his next wife, and STILL wants her to acknowledge him as head of the church and declare herself illegitimate. (In)famously, one of the nobleman Henry sends to his oldest daughter to make that clear tells Mary that if she was his daughter, he'd smash her head to the wall "like a boiled apple" for her disobedience. (In fiction, this man is invariably the Duke of Norfolk, since he was one of the men and was just the kind of jerk to say something like this, but in truth we don't know which one said it. Just that it was said, courtesy of Thomas Cromwell receiving a report of it.) This is when Mary caves, which she'll never forgive herself for, and acknowledges her father's supremacy.
Once Henry is dead, both of the Protectors reigning for young Edward VI are very Protestant, and Edward as he becomes an opinionated Tudor teenager turns into an ultra Protestant, so it's more harrasment from a royal relative for Mary. And then Edward dies, and after the nine days Jane Grey interlude, Mary becomes Queen to a universal wave of popular acclaim. She's the daughter of the beloved Katherine, the true Queen, she's the true heir, persecuted for years but still there, she's the people's princess finally becoming Queen! And then, alas... it turns out that of course the faith Mary has clung to through all these years as one of the few things to cling to as everything else was taken away is no longer the majority faith of the country, and her attempt to turn it all back to how it was when she was a child so that she saves her subject's souls and redeems her own moment of weakness (as she sees it) can't be done without using more and more violence. The marriage she makes to one of her Habsburg relatives, those relatives she saw as her defenders all through those miserable years, is spectacularly unpopular among the English, contributes to alienating her from them, and while cousin Philip is perfectly polite to her, he doesn't love her while she falls in love with him. Does he develop a thing for her younger sister? We'll never know for sure. If so, it's an additional wound, but I think worse is that she can't give birth to a child. (Since Philip already has Carlos, it's clear it can't be his fault.) When she dies, she knows that her attempt to make England Catholic again has failed, as Elizabeth sure as hell won't continue in this vein, her marriage has failed, and the people have gone from loving and supporting her to hating her.

As I said, it's an incredibly sad and tragic life, and the tragedy wasn't lost on Elizabeth who told the Venetian ambassador once she'll never name her successor since people always favor the rising sun over the setting sun and she won't forget how they deserted her sister in droves. (Not to mention that the Mary/Philip marriage illustrated the drawbacks of marrying a foreign prince just as Mary Queen of Scots' second and third marriages illustrated why marrying a local noble isn't much better.) Now Mary wasn't literally alone when she died - she had some very loyal ladies-in-waitings with her, one of whom, Jane Dormer, married a Spaniard, left England and thus contributed with her own writings to a positive image of Mary that's very different from Bloody Mary as written about in the English tradition. Now, none of this makes the people burned during Mary's reign less burned. But it's very easy to imagine Mary, if just a few things in her life had turned out differently, or she had lived in a previous century, becoming a beloved Queen instead of a reviled one. In any event, her father's treatment of her easily rivals FW's of Fritz. And there's no evidence she was hostile towards Elizabeth up to and including the start of her own reign, though undoubtedly there were all kind of repressed things lurking in her subconscious, but the fact Elizabeth was illegitimized and ostracized by Henry as well and that Mary by all accounts loved children (the age gap between her and Elizabeth was big enough that Elizabeth could have been her daughter if Mary had given birth at 16 or so) makes it plausible that for as long as Elizabeth was a child and young teen, they got along. Mary even invited Elizabeth to live with her after Henry's death, and if Elizabeth had done that, the Thomas Seymour desaster could have been avoided, but of course from young Elizabeth's pov, living with Catherine Parr instead was a no brainer.

In conclusion: have a vid that sums it up as well.

ETA: And here is another vid about the Mary & Elizabeth relationship in its complexity, this one based on a different series, Becoming Elizabeth.