Aries didn't detail everything to Abel about her current dilemma. However, she did give him hints. Abel was smart enough to put two and two together. He would figure it out on his own — it wouldn't be an exaggeration if he already did.
Abel only asked Aries one thing, and that was to get things done. For her to uncover the truth and make amends for this personal dilemma. There wasn't any good thing in this situation, but if there was, it was that she expected such underhanded means from her enemies to shake her.
Thus, she came face to face with Miguel to prove to herself that Miguel Rothchild simply stole her brother's face. That Miguel and Davien were two different people; the former's face was simply an illusion or some sort to deceive her.
After all, Aries was the only person who knew what Davien looked like.
