Isabel smiled back at Rogue confidently. Some of it was bravado. Isabel had no real idea if her brother would even be able to help Rogue or not. Max had healed plenty of humans but he had never tried to heal a mutant. And it was possible that Rogue's condition wasn't healable and that Max wouldn't be able to do anything about it. But she didn't want to let any negativity in. She had to stay positive and focused for Rogue.
She put her hand on Rogue's shoulder and gave it a small comforting squeeze. "We talked a little bit about what you can do already," Isabel told her. She had been the one to approach Max about healing her so they had already talked about what was going on at least in a general sense.
"I told him that your power allows you to absorb other peoples' powers and their memories and personalities. It started with your dreams and now it's starting to happen when you're awake too. Right?" Seeing Jimmy in the dream had been completely foul. Isabel was only too happy to watch that jackass get what was coming to him. She hated that Rogue had to carry around all his filth with her though.
She felt the teensiest bit bad about slapping Rogue across the face but when she had been acting like Jimmy it was an easy instinct to follow. It had also, luckily, snapped Rogue out of it. So in the end she had made the right call.
She turned to Max. "She's a mutant so it's in her genes but I'm not sure if it's a physiological problem." Implying that it may be a psychological one. Isabel didn't judge Rogue though. Everyone had their issues in a zombie apocalypse, some more than others. Some people didn't have pyrokinesis and telekinesis to fight off zombies and humans with. The problem with that was if it was a psychological problem it was a good bet that there would be nothing Max could do to help.