You did it! We figured this one out! It is a truth universally acknowledged (by me for certain) that the Bitchery pretty much knows everything, and really, it's true. Scroll down to see the solution for this HaBO - and many thanks!

This HaBO request comes from Kelli. It’s a historical she read back in high school:
I have been struggling to remember the name of this book for quite some time. I read the book when I was in high school, so it is at least 25 years old and is probably older. I believe I picked it up secondhand.
It was a Regency romance where the heroine is a ballerina. Her mother has recently died and she doesn’t have much money. I think her mother was English and her father French and that the beginning of the book, at least, takes place in France.
The manager of the ballet asks her to join an after party where she is attacked by a man. She calls for help and an Englishman walks by. He ignores her until she calls out in English. Then he saves her and takes her back to his house. He decides to be her “protector,” but I don’t think they have sex. She is very childish and is supposed to stay away from his guests. Then, one day, a man who she identifies as her uncle visits the hero. When she sees her uncle, she runs up to him. It turns out she’s from a prominent English family, so the hero marries her. I think her uncle wasn’t actually a relative but an honorary uncle. I don’t remember anything else about the book.
Also, I hope the hero redeems himself for not immediately helping the heroine!

There is a Goodreads listopia with ballerina heroines but only a handful appear to be Regency era:
https://www.goodreads.com/list/show/39893.Passionate_Pirouette_Romances_With_Ballerina_Heroines
That sounds like such a Mary Balogh plot but it doesn’t look like she wrote any ballerina heroines.
Eva Ibbottson wrote A Company of Swans that centered around ballet. But I think they were later than Regency. I think late 1800’s. Her writing was very memorable.
This sounds like a Barbara Cartland I remember reading sometime in the late 1980s.
I agree this sounds like a Barbara Cartland kind of plot. I don’t recognize the book. But if you want a good Regency about a dancer: The Opera Dancer by Sandra Heath. I don’t think it’s available as an e-book but there are used copies around.
Does seem very Barbara Cartland!
Margaret Evans Porter wrote several Regencies about entertainers, including one about a ballet dancer who marries a duke (Dangerous Diversions). Quite good, though I really prefer Toast of the Town, about an actress. Porter knows a lot about the history of theater and dance–all woven into her plots.
Barbara Cartland’s The Passion and the Flower is about a ballet dancer and a Russian prince, but it doesn’t sound like the right plot.
Ok, I’ve no idea although for some reason I thought of Jane Eyre even knowing that was wrong. Would like to know.
IT’s not A Company of Swans but I definitely recommend that Ibbotson and A Countess Below Stairs
Ok, this seems quite familiar. I read one where she’s a dancer, from Paris, and quite devoted to art, but in London ballet’s just about showing your ankles and entertaining men, so the hero doesn’t understand at first how pure and innocent and ultimately well born she turns out to be. I don’t know the name of it or anything, and those details (if details is the word) may not be relevant, but if that sounds right I can try to dredge up more.
@kkw, You may be thinking of Ways to be Wicked by Julie Ann Long. She’s a respected ballerina in France, comes to England to find her long-lost family, and ends up in a burlesque hall until she’s reunited with her family.
Sorry, somewhat off topic but Erin Satie’s Young Bloods quartet has a ballerina heroine. It’s the first book in the series and the hero is into boxing.
A ballerina in THE REGENCY?? Surely this is a Victorian-era book (or else the author did bad research). Ballet in the Regency was… not ballet as we know it.
Kelli has found her book! It’s The Dancing Doll by Janet Louise Roberts, and it looks like it was published in the 70s. That may have been why it was a tough find.