socialite

That's probably meant to be Mrs. Charles DeLoosey Oelrichs, a prominent member of Newport society and a member of the Congressional Union for Woman Suffrage too. She married Charles DeLoosey Oelrichs (1882-1973), a stockbroker, in 1907, and they were divorced in 1921.

They had one child, daughter Margery (aka Marjorie, aka "Bubbles"); maybe that's her in the photo. If it is, she eventually married Eddy Duchin, the bandleader, in 1935, and became mother to Peter Duchin (b. 1937). Marjorie Oelrichs Duchin died two days after the birth of Peter.
en.wikipedia.org/wiki/Marjorie_Oelrichs
en.wikipedia.org/wiki/Eddy_Duchin
en.wikipedia.org/wiki/Peter_Duchin

The Mrs. Oelrichs in the photo above does not appear to be the same woman who, in another Bain/LOC photo, also is identified as Mrs. Oelrichs. Perhaps Bain made an error in one of the identifications. Moreover, the daughter in the other photo (who does not resemble the girl in this one) is identified as "Margaret," not "Marjorie." Here is the other photo:

Indeed, Wystan, this woman and daughter look more like the mother and daughter in the pictured labeled as Mrs. Amos Pinchot.
www.flickr.com/photos/library_of_congress/4037482176/
The daughter, in particular looks to be wearing the same hat.

www.newyorksocialdiary.com/node/136306
has pictures of Gertrude Minturn Pinchot that look like this woman, but is mainly about her daughter, who was the actress Rosamond Pinchot. Pictures of Rosamond as a girl on the web page could certainly be this girl.

The Oelrichs seem like a complicated family with a lot of same-named people; Margery/Marjorie Oelrichs, daughter of the Charles DeLoosey Oelrichs, was born after 1907, which would seem to make her a little younger than this child.

I like the alternate identification--they do look much more like the Gertrude and Rosamond Pinchot in the photo swanq links to. Not only the same hat on the girl--looks like it could be the same dress, socks, and shoes too!

A Newport socialite named Miss Edith Mortimer married Count Mario di Zoppola, an Itaiian aviator, in 1919, at her parents' country home in Wheatley Hills. Her mother was Eleanor Roosevelt's aunt. The Count and Countess di Zoppola divorced at Reno in 1929. In 1937, Cole Porter was badly injured while riding at Edith di Zoppola's Oyster Bay estate. Miss Mortimer seems to be enjoying "chair skating"? A G. MacCulloch Miller was mentioned winning a "toboggan challenge plate" in a winter sports event at Tuxedo Park in 1913. (George MacCulloch Miller had a daughter Edith too, but she announced her engagement in 1902.)

Looks like a better way to "skate," with less risk of falling. LOC: Spelling error: MacCulloch has an "a" in it.

This is Miss Marjorie Brown (1892-1988) of Atlanta.

Marjorie was a daughter of First Lady Ellen Wilson's cousin, Colonel Edward T. Brown of Atlanta. She had two brothers, Edward M. and Henry W. Brown. [1] [2]   Growing up in Georgia, Marjorie was a long-time childhood friend of Jessie and Eleanor Wilson, and she later shared her college years with Jessie in Princeton.

Marjorie attended Miss Jessie Wilson as one of five bridesmaids at her White House wedding to Francis B. Sayre in November, 1913, and she was also a special guest at the wedding of Eleanor Wilson, six months later at the White House. [3] [4]   A portrait of Marjorie Brown appeared in The Atlanta Constitution on November 9, 1913. (shown below)

Marjorie married Benjamin M. King in Washington, DC, in December, 1920. Miss Margaret Wilson, daughter of the president, was maid of honor, and former First Lady Edith Wilson was among the guests. [5]

Benjamin King had been engaged to Eleanor Wilson. He was the manager of a lumber camp near Madera, Mexico when Eleanor met him while traveling with friends in 1913. The President and Mrs. Wilson liked King and approved of the engagement. However, Eleanor broke the engagement when she met William McAdoo later in 1913. Wilson and King remained friends, and after Benjamin and Marjorie married they would visit the Wilson’s. [6]

 
"Miss Marjorie Brown" by Meade

 

Simple, elegant, and there is something about those beautiful eyes.

A Timeless Treasure, for sure!