I think she is wrong in doubting Zain at all. Since this whole situation began she hasn't given Zain even an opportunity to speak.
She questions him and she answers the questions herself. Even yesterday when Gauhar said Zain threatened her, she just believed it, and started accusing Zain without even asking him if he actually even called Gauhar. She doesn't even consider that Gauhar could be lying about everything, but doubts her own husband straightaway.
I'm really disliking this storyline, it's like Aaliya has lost all her thinking capabilities. The fact that Aaliya and Zain trusted each other and actually communicated with each other, was one of the reasons I liked this show. The way they're portraying Aaliya at the moment is ruining things however. I hope she comes to her senses, yes Zain hasn't always been perfect but it is true that he has stood by her on almost all occasions, but now it's time for her to support him she doesn't even listen to him, forget trusting him.