So far, all I can find is the Married Women's Property Act of 1882. My understanding is that there WAS no loophole for an unmarried woman to own property -- but could she inherit property if the guys dies, and have everybody leave her alone? Could she dress in drag in she had a low voice? Use a pseudonym and never meet up with the real estate guy...? Would she have to find a man she trusts to buy it for her?

I think you're missing what the Married Women's Property Act was about. Under English law from the Middle Ages on, a married woman was literally "covered" (couvert) by her husband's legal identity: any property or money she owned was his, and any sales or purchases she made without his consent could be retracted at his request, because it wasn't her money to spend/her things to sell. An unmarried woman was sole - alone, with her own personhood under the law. So earlier in the nineteenth century, an unmarried woman could inherit property, start a writing/acting/singing career, etc. and accumulate money, buy a house ... and then if she got married, she lost her right to control any of it. If she went on tour as a soprano in Rigoletto after she got married? Her pay was her husband's.

Now, in practice there was significantly more leeway and variation in how it played out. Men were not all tyrants who deliberately stripped their wives of all agency. But under the law, any man could be an abusive tyrant with next to no consequences. The Act was developed to protect married women from abuse from husbands who would exploit this system and to give them some basic human rights, one of the first victories of a long struggle for recognition that wives should not be subject to their husbands in every way.

Unmarried women did not need a loophole to own property, because they were the loophole. Some at the time might think that young unmarried women should be under a man's guardianship, but as long as they were of age they had the ability to make business transactions. Your heroine doesn't need to pretend to be a man, she just needs to be 21 or older.

I have some previous answers on this for more information:

Jane Austen and the Brontes are among the most treasured voices in the English language despite having published anonymously at a time when married women weren't permitted to enter into contracts.Were there any role models for women writers of their generation?Did their prominence affect these laws?

I'm watching Gentleman Jack and I had a question. Was it common for a 19th Century British woman to be as active an industrialist and businesswoman as Anne Lister?

In Victorian England, who would gain control of a woman if all her close male relatives passed away?

Victorian Era Women's Rights in Estate Ownership through Wills/Contracts

If you have any insight as to where to find information about professional dominatrices in Victorian England, I'm having trouble finding any info about them, as well. If there were any.

I've read of them in the eighteenth century, so I'd bet there were! Most of my books on the topic of sex work relate to the Middle Ages or eighteenth century, but I have a few titles to recommend:

Prostitution: Prevention and Reform in England, 1860-1914, by Paula Bartley (Routledge, 2000)

Common Prostitutes and Ordinary Citizens: Commercial Sex in London, 1885-1960, Julia Laite (Palgrave Macmillan, 2012)

Their Sisters' Keepers: Prostitution in New York City, 1830-1870, by Marilynn Wood Hill (University of California Press, 1993) (Not England, of course.)

This article seems to suggest prostitution was legal, but every piece of academic writing I've found tells me that it wasn't, so if somebody would be so kind as to ELI5?

Julia Laite explains it pretty well: basically, it was not illegal to sell sex in England, but the authorities cracked down on it by attacking how it was done. It was illegal to run a brothel, for instance, and that could be defined as loosely as two roommates bringing customers back to their flat. Public indecency was illegal, so dealing with customers outside could get you arrested. And so on. The Contagious Diseases Acts meant that women suspected of being prostitutes could be detained and forcibly checked for STDs, and imprisoned in a hospital if they were found to be infected. (Just being detained on suspicion could be enough to ruin a woman's reputation and force her into sex work, of course.)