A girl named "Bell" appears regularly in the Powell family adventures in Leesburg, VA in the 1840s but it has been difficult to identify her because the name Isabelle is common in Leesburg. However, through the meticulous process of my database of names and references in letters combined with my research, I have finally been able to identify her. Her full name was Isabella Kennedy Eskridge. Her parents were Charles Guley Eskridge and Margaret Pope Eskridge, and the family is listed as living in Leesburg on the 1850 census. Their home is noted on the Yardly-Taylor map of Leesburg dated 1854. That map has an inset of Leesburg in the upper left corner, and the home of "C. G. Eskridge" can be seen on the north side of Cornwall street.
I was able to confirm Bell's identity using my database of names and footnotes. I filtered this database down to every mention of the name Bell in Leesburg and then read through every reference. In one instance, Mrs. Powell mentions visiting a Mrs. Eskridge and notes that Bell is unwell and spitting up blood again. As horrifying as this sounds, it is mentioned regularly in the letters such that it appears not to have been uncommon. This account tells me that the Powells know a "Bell" with the last name Eskridge. The 1850 census record noted above tells me that Isabella Eskridge is a year younger than Hattie, which makes her the right age to be friends with both Hattie and Rebecca. So, she became a stronger contender than the other Bells. Next, one of the references indicated that Bell's grandfather died in 1849. I was able to determine that Bell Eskridge's grandfather on her mother's side (John Chapman Hunter) died in 1849, so both references were to a Bell Eskridge. I then read through all of the references to pick up on nuances between how the different girls named Bell were referred to and was able to determine that the vast majority of their interactions with "Bell" were with Isabella "Bell" Kennedy Eskridge.
There is another Bell in town by the name of Bell Gray, and she is also well known to the Powells. Bell Gray is about 25 years old at the time (based on the 1850 census), and the Powell sisters usually refer to her as "Miss Bell," due to her being a bit older. Further, the accounts of "Miss Bell" in the letters seem consistent with a woman of 25 instead of 16 (meaning, she seems to have matured beyond the shenanigans of the younger girls). Therefore, through the study of the context of the letters, the differences in how the two women are referred to, and the timing of a grandfather's death, I could eliminate other "Isabelles" in Leesburg and confirm the identity of Bell Eskridge.
Bell Eskridge was born in 1834. She had an interesting life and filled a lot of different roles. After the Civil War, she is listed on the 1870 census as a music teacher, so she was clearly musical and well thought of enough to teach. By the 1880 census she is living with an uncle and his family while working as a seamstress. The census notes that her uncle is 72 and paralyzed, so she is likely an instrumental member of the household. By 1890 she is an assistant matron at Louise House - a home for impoverished women in Washington DC where she's likely using skills she gained in the household of her Uncle. According to the website of the surviving entity that exists today, Louise House was founded and funded by a Mr. Corcoran in about 1870. His goal was to support and provide a home for impoverished elderly women. That home endured and exists today (after combining with other entities).
By the census of 1900 and 1910 Bell Eskridge is still at Louise House, but appears to be a resident instead of a matron. She died in 1918 and is buried in an unmarked grave at Oak Hill Cemetery in Washington DC where the location (per findagrave.com) is Lot 316, Plot 32. Interestingly, her mother is also buried here in an unmarked grave.
Despite the unmarked grave, Bell is immortalized in the Powell Family Papers and remembered as a sweet friend to Hattie and her sisters in Leesburg. I don't think it would have surprised them to know that she appears to have spent her life devoted to the education and needs of others.
Painting is, "Gathering Lilies" by Eastman Johnson, 1865