Have you tried Googling? “tarot high priestess nimue” brings up the first one in the first result: it’s Legend: The Arthurian Tarot by Anna-Marie Ferguson. Any time a card has something distinctive in its naming or imagery, a Google search for those will usually find you your answer.
Edited to add: do you have a physical copy of the book? I just checked my copy and all of the decks featured on the cover are noted on one of the first few pages. The other two are Lisa Hunt’s Shapeshifter Tarot, and The Quest Tarot by Joseph Ernest Martin. Glad I could help!