Miss Burke's Secret. Fair Tales of the Regency, #1

Twelve years of being forgotten taught Elinor Burke to accept invisibility. It was safer that way - and she was content. Until her stepmother arrived with a scheme: pass off her own daughter as Ellie, steal the inheritance Ellie never knew existed, and silence the real heiress with a threat of Bedlam. Ellie is outraged, but she's also a woman with no education, no proof, and no reason to believe anyone would listen.
Alexander Turner came to Berdwell Manor to prove himself. As steward to his cousin the earl. As the brother who will finally save the sister he failed to protect. When he uncovers the truth about Miss Burke, he sees the woman everyone else has overlooked - and he believes her. But the earl wants the matter dropped. And Alexander's sister is still missing, vanished after her husband had her hospitalized for "low spirits." Pursuing the truth means risking his position and any chance of finding her.
When her stepmother's physician arrives to take Ellie away, she has one chance: don a mask, flee to the masquerade ball, and do the one thing she's never dared - speak up and demand to be heard. Even if no one believes her. A wholesome Regency romance about finding your voice, claiming your future, and the steadfast man who saw you all along.