Allen was watching Anna from the back when she was talking with Harry. He didn't hear anything, he didn't see her face and her reaction but he is so angry that Anna is talking with Harry.
Allen started to imagine that Anna is still in love with Harry and that is the reason, she is talking to him. He is so jealous imagining so many things like she is going to leave him for Harry and etc. He can't take it anymore and the alcohol is not helping at all.
Anna hangs up the call and walks back inside and saw Allen's reaction, she felt something is wrong with him but she didn't bother to ask anything. She just walked towards the table next to thier bed and places her phone. Then she walks to the other side of the bed, getting ready to sleep. Anna is only wearing a long and comfortable T-shirt and shorts.