I'm aware most American Fire Emblem fans mostly focus on the games that come out in the U.S., and that is fine. Unfortunately, the one setting Est comes from is from Archanea. When Shadow Dragon hit the U.S., it quite frankly sucked. New Mystery of the Emblem: Heroes of Light and Shadow was the second DS game that was a remake for Archanea, based off Fire Emblem 3. In other words, let me clarify things here.
Fire Emblem: Dragon of Darkness and Sword of Light (Shadow Dragon)
Fire Emblem: Mystery of the Emblem (New Mystery of the Emblem: Heroes of Light and Shadow)
One is the sequel to the other. For general DW use, I picked the latter of the two. She is post-game Est, where things are wrapped up and she vanishes after leaving Abel. After some revisions, I also inputted what I've gathered from my character review of SoV.
2) Has the mun played other characters before that could fit in a potential DW RP home?
This is the tough part. While its true, even the mun themselves sort of agrees with most game mods that hoarding canonmates just to playercest defeats the purpose of roleplaying on DW in the first place.
Aside from Fire Emblem, they have. Right now she's just barely getting back into DW RP in general so it may take her a while to figure out who to field out.
3) I wouldn't want to make you sad, but would Est be subject to dying/getting raped/etc etc.?
Consult here carefully. :) If you read here and wonder, you will already have my permission to...
Kill her? Nope! Or at least, NOT RIGHT AWAY.
Rape her? Depends on who's trying it
Have an affair with her? Yes
Befriend her? Of course
Hate her? However you wanna play that is fine
Capture her? ...she's always getting captured, why not?
4) How many times has Est been held hostage?
THREE. Once in FE1/Shadow Dragon, once in Fire Emblem Gaiden/Shadows of Valentia, and once in New Mystery. If you ever play the translation patch for the third game, Palla even remarks about this! But don't rub it in on the poor girl, please.