So Beruka reveals that her foster father, who worked at an assassin's guild, was responsible for the murder of Oboro's parents, and the reason he did so was because Oboro's parents were successful merchants and thus had close ties to Hoshidan nobility, so they weren't just random targets from the beginning. When Oboro asks where the man is, Beruka tells her that she (Beruka) killed him out of a contract once she started taking her own assassination jobs. Knowing Oboro feels upset that the killer is dead, Beruka offers herself to be killed; she says,
"I killed the object of your hatred. So you should hate me instead. It has to come spilling out somewhere. You need someone to get revenge on. I don't think you can go on for long without a scapegoat."
Oboro refuses and tells her that she won't kill her because, while she is racist and hates Nohrians, she knows Beruka is a victim (Beruka tells her about how her foster father never her treated like a daughter, only as an assassin), and... well, I'll just show it via pictures.
I don't know about you, but for someone who is racist towards an entire nation, not wanting to kill someone because you know it's only going to lead into more hate is a huge...
HUGE step. Admittedly, it's a very difficult step to undertake when you have animosity towards something, so to see someone like Oboro pulling this off is something I applaud her for her, and she solidified herself within the top 10 of my favorite FE: Fates characters at this point.
I guess that's another reason why she managed to make the top 4 of the females in that character popularity poll. I'd say it's also that support conversation is also one of the best in all of Fates.