Eileen’s past is a troubled one. She found out about her own mother’s murder (Marina - almost certainly killed for daring to speak her mind) only in early adulthood. Nobody had wanted to speak about it partly to avoid upsetting Eileen, who showed she knew her own mind from a very early age, but also because it was suspected (though never properly proven) Marina’s murder was akin to a politicial assassination. Eileen swore to herself she’d uphold her mother’s reputation for truthfulness and belief that justice was worth fighting for. Marina, certainly up to her daughter’s defection, would be proud of Eileen.
Eileen still hasn’t told Jennifer anything about her grandmother’s past as Eileen fears Jennifer will think she’s trying to use this to exploit the girl. Eileen is vulnerable where Jennifer is concerned. Anyone else and she’d happily exploit them but not her own daughter. Eileen would at some point like to campaign for a proper statue to be put up to commemorate her mother but knows she is unlikely to get this out of the Queen unless she agrees to returning to the Kingdom at once. FNN did once do a brief biography of Marina as part of their royal series but her sudden, unexpected death for whom nobody was ever brought officially to account, meant they could only give out sketchy information.
Marina’s death was never officially investigated, which is unusual in the realm’s long history. It is unique given her royal (by marriage) status. There was no question of her death being anything but murder. It was left to Eileen, as she matured, to look into the matter and deal with the culprits as she saw fit. They were her first “kills”, though she saw it as the executions which were unaccountably delayed. Eileen does not blame Roxannadrell - the latter was not on the throne but her mother, Eileen’s aunt was, and even Eileen sometimes thinks there are things so deep they’re best left buried.
Marina was not the only troublemaker to be got rid of as over the centuries various beings who asked awkward questions ended up dead in a variety of ways. This was why Brankaresh was so hopeful Eileen would get her comeuppance without him necessarily having to do anything about it. He forgot in Eileen’s being out and about, talking to people, getting rid of obvious threats such as dragons and trolls, she was enormously popular. This gave Queen and Council a dilemma too. There was a limit as to how far they could rein Eileen in, given they didn’t want to upset the populace either.