SOLVED. Fantasy novel set during the reign of Charles II [s]

[Caitlin]

I am asking on behalf of my mother, she read the book in the last few years and thinks it was published sometime since 2000.
Set during the reign of Charles II, starts at a country estate at the time of the plague and follows a female protagonist to London where she experiences the great fire of London. There is also a death at the Frost Fair on the Thames.
There are elements of witchcraft.
The protagonist is associated with a member of the court, not sure whether an actual historical character or fictional...
There might be something to do with fairies, but not sure whether this is a major component of the story or not,
Any suggestions would be much appreciated.

[Caitlin]

I'll add that she thinks the author is female and she read it in paperback. Title or cover could have something to do with a moon or tree.

[Lou]

This is what I scrounged up. It is the third of a series, but it's fantasy, includes Charles II, and plague (the summary says pestilence, same thing). None of the reviews go into great detail, so I don't know about the rest.

Darkwitch Rising

[Caitlin]

I've actually read that one so I know it's not it, although when she first described it to me I did think of that book.
I'm not sure that Charles II is a hugely prominent figure in the book...
I'll see if she remembers anything else, thanks for looking into it :)

[caracal-eyes]

Some possibilities:

Lady of the Butterflies
Year of Wonders
The Apothecary's Daughter

I'd say that Lady of the Butterflies looks most likely to me, but I didn't find anything that stood out as a perfect match.

[Caitlin]

I think we have worked it out and it was actually 2 books she was mixing together...
One of which WAS Darkwitch Rising, hence the link to Charles II but the other was another Sara Douglass book, The Devil's Diadem:

https://www.goodreads.com/book/show/9...

Nothing to do with Charles but has a plague and her father came back from the Crusades, which my mum had initially mentioned but because that was happening at the time of Charles II we dismissed it!

Thanks for the help and for those book suggestions which I think I may go look up!