While this has a trope I'm not fond of - our heroine has retained her accent and holds herself like a member of the upper classes, I would say this would be hard to do and often is rubbish, people like to blend. Apart from that it's a fun read that I found hard to put down. (another bad decisions book club book).
Annabelle Smith works as a healer in Whitechapel and was surprised when Lytton Staines, Earl of Thornton turns up on her door... his sister is suffering from some sort of wasting disease and he's exhausted regular medics. She comes recommended by servants. When they meet the impression is ruined by the pet dog who rips his waistcoat and spills tea on him.
The two of them are an interesting couple and it was a fun read. There were bits that stretched credulity but overall it was a good read.