Continuation of spoiler talk:
In the LN, I'm pretty sure he puts her up against Igrit first, whom she beats. Then she pushes to fighting the truly "strongest" of his summons saying something along the lines of "I wanted to fight it one more time". So it came from her decision to fight Beru.
more spoiler talk lol:
yeaaaaa i think i remember she got upset that he put out igrit and was like "theres no way this is the strongest, are u insulting me?" and he was like "fine! u asked for it"
additional spoiler talk:
i dont remember if she knew he had the ant king tho
Additional spoiler talk:
She did know he had Beru. If I'm to reference what I read in the LN, she says that she knew since she watched the footage of the raid so she saw him resurrecting the ants to fight for him and putting two and two together, he would have resurrected the ant king to fight for him too. Going back to my earlier reply of "I wanted to fight it at least one more time", the only 2 raids Jin-Woo and Hae-In have been in was the raid with the High Orc Shaman (Tusk now) and the Jeju Island raid.
AHA u were right
he really pulls a dirty move on her during this test tho..... so mean
spoiler:
he literally has her go against the ant king, knowing she has trauma and shit