Her Desperate Masquerade. Regency Magic Faerie Tales, #8.5

Miss Lizbeth Sandiford has done everything she could for her ill mother, even finding work as a housemaid for Lord Sterling when the doctors' bills depleted their finances. She doesn't know what else to try, until she hears a rumor of a viscount who has spent time in Faerie. George Cole has inherited the title of Lord Sterling, but he wishes it came with less matchmaking from his mother. The guest list for his birthday ball is too full of simpering, unattached ladies.
All he wants is one who will hold his interest and inspire the kind of lifelong devotion that his late father never showed. Attending the masquerade ball is Lizbeth's only hope of meeting the viscount and discovering if there could be a fae solution to her mother's ill health. But is a mask enough to hide her from recognition by her employer? And could a single dance with him be enough to doom her heart, even if she does manage to save her mother?Her Desperate Masquerade is a short standalone novella retelling of Cinderella.
It has a complete HEA and can be enjoyed without reading the rest of the Regency Magic Faerie Tales. It also serves as a series epilogue, so it includes cameos from characters from the other books in the series.