Beato wear dress is younger sister , that's Beato revived by battler but she doesn't remember anything . She wanted to find "herself" in pass to have Battler's love. And she found her elder sister , that's Beato tested Battler in Ep4
In Tea party , Beato became Battler's wife (and a true Tsundere) .
That all i know
I have a program can trans visual jap => eng . Althought i don't know jap but i can read normally