In the end, Alaina decided not to ask him any question regarding his actions towards Aria last night for now. It is not like he would tell her all about it anyway.
Besides, she wasn't sure if even she was ready for the truth.
Alaina was all alone in here with him, if there is something off about him –which she was beginning to think there definitely was something going on here– she didn't want to know about it because knowing about it would also mean he would know about her knowing and who knows what he might to do her.
If his truth turns out to be something she doesn't like, something unsettling, would she be able to handle it after he explicitly have told her she can't leave for now.
She will not let her curiosity kill the proverbial cat tonight, especially when in this case she herself was the cat. Ignorance is bliss as she will remain ignorant till she can get out of here.