she already knows the results of the last exam. so to avoid a fuss and raise affection flags to prince rodd, she tried to do the third test which involves measuring her magic and element by going lowkey (missing the target on purpose and going away as soon as the tool regiatered her magic).
i forgot what its called but Rei, being the heroine of the otome game, has really strong (top tier if you may) water and earth magic. she's a rare case of being able to have dual attributes at maximum affinity,
I kinda wished she had Lightning release because as a transmigrator she could fully use its potential(a bit like Misaka Mikoto)
Also her name is Rei , kinda fits