Lie to her

"Yes... I ended his life." You reply, hoping that by lying to her you might gain some more information...

She quickly gets up, runs towards you and embraces you, "Thank you so much, my prince... I.... I thought he was going to kill me!"

You notice how relieved she is with the thought that the assassin is no longer after her. Hopefully by not fearing for her life she won't hesitate to tell you more about Enzo...

"But regrettably I lost my sister in the fight..." You say painfully.

She looks up into your eyes and says with empathy, "I'm so sorry my prince, even though I just met her I know you two were... Well close..." Looking away she adds, "But since Enzo cant come after me anymore I have something to tell you..."

Smiling as your plan starts to take effect you put your hand on her chin, gently pulling her to face you again as you reply with interest, "Go on..."