Scribe Yearling

 is a member of the Capital Wasteland Brotherhood of Steel's Scribes. She can be found front desk area of the Arlington Library. She is related to the The Wasteland Survival Guide quest. Also when speaking with her upon entering the building for the first time, if she is spoken to nicely she will offer you 10 XP and 100 caps for each Pre-War Book you take to her. 10 books are in the building she is in and many others are scattered through the wasteland.

Bugs
It has been known for her to just disappear and not be found again. She will move about the building to some degree, sometimes sitting at a counter upstairs and wandering around the corridors. She also has a bed on the second floor near the left staircase.

Oddly, she doesn't seem to recognize Pre-War Books bought from vendors (e.g. Crazy Wolfgang). They're left behind and not paid for after a "here's all the Pre-War Books I have" transaction. If approached with only those in the player's inventory (and none the player just picked up out in the world somewhere), she responds to "I have Pre-War Books for you" with her indignant "you do not, stop wasting my time" response.