So This is Love (A Twisted Tale #9) by Elizabeth Lim

What if Cinderella never tried on the glass slipper?

Unable to prove that she's the missing princess, and unable to bear life under Lady Tremaine any longer, Cinderella starts work at the palace as a seamstress. However, when Cinderella finds herself witness to a grand conspiracy to take the king--and the prince--out of power, she is faced with questions of love and loyalty to the kingdom.

Cinderella must find a way to stop the villains of past and present . . . before it's too late.