Here's why:
* Her upbringing: Blackwell was born and raised in England, attending schools there. RP was the standard accent of the upper and middle classes in England at the time.
* Her social standing: Though not wealthy, Blackwell's family was educated and valued social standing.
* Her profession: As a doctor, she would have interacted with patients and colleagues from all social strata. However, the medical field in the 19th century was dominated by the upper classes, making RP the likely accent she would have adopted or maintained.
It's important to remember that accents can change over time, and even within one person's lifetime, but based on the available information, Elizabeth Blackwell would have spoken with a British accent, likely RP.