Call her childish for being afraid of a scene caused by her overactive imagination, but Islinda was not intent on having another panic attack while alone. She hasn't forgotten what the first time felt like.
Islinda thought she was going to die, there was just this sense of impending doom that made the panic attack worse and much more intense, especially recalling how helpless she had felt in that room.
And then her heart was pounding so much faster it felt like it would pop out of her chest. She was choking on her breath and her throat was painfully tight. All she could hear was her blood pounding in her ears, which drowned out Aldric's voice until that sharp slap jerked her back to reality.