I have a book I forgot the title and author of, would love some help if someone recognizes this description.
Its situated in London, England about the 1800's probably late 1800's
both main characters are of the peerage.
The situation as the story opens is the main male is thinking of offering for the main female's Older Sister in Marriage. The Main female, a young lady about 18yrs, goes to the home of the main male, a gentleman of the Ton, in order to talk him out of offering marriage to her older sister. She tells him that her sister is already in love with another but because her sister is a dutiful daughter her sister will throw away her happiness and marry him at their parents request. She asks that he instead offers for her, the younger sister, since her sister finds the gentleman a bit intimidating. The gentleman of course is a peer and older about 30 to 35, and at first he is against this idea but then starts to think that with this younger sister his life will never be boring.
Later on in the story the main female has a confrontation with a tradesman when the man attempts to abuse a dog. She stands up for the dog and is nearly hit by the man. After this a constable gets involved the tradesman makes accusations against her and makes a comment about her lack of sanity after she blurts out that she is engaged to the main male, and they end up going to see the main male at his town house and have him verify her identity. She ends up asking him to take in the dog since he will not be allowed in her father's townhouse. Of course after a very short time the dog becomes attached to the main male.
I know this is alot of details but i thought the specifics might make it remember-able to someone.
Also the person her older sister is in love with is the vicar in their home town.