Allison's realisation wasn't due to Vanya or Five, it was actually due to Klaus. Since being back Klaus had struggled with his addiction. It was weird since they were thirteen and Klaus hadn't started drugs until he was fourteen. Five had explained that resetting the timeline could result in phantom pains. It was a strange analogy but Allison kind of understood it. They had lived completely different lives in the future, hell in the future Vanya rendered Allison speechless. Even now she could still feel the pain in her throat and had to remind herself that it wasn't real.
So yes, whilst Klaus wasn't actually going through withdrawals he felt like he was. As such Vanya and Ben had been his constant shadows. They were there when he felt like he needed a hit but couldn't get one. Allison supposed she shouldn't be surprised. Ben had followed Klaus around as a ghost and Vanya was always the most caring of them, despite her future actions. As such, she had taken to providing Klaus with an alternative to drugs. They would play childhood games and whenever the pain got too much she would stay by his side, whispering soothing words. Ben, on the other hand, would keep Klaus away from their father and tell him how well he was doing. It never occurred to Allison how much time he and Vanya spent together until she spent most of their time with Klaus.
It never occurred to her until she bumped into Five in the hallway, he seemed dishevelled. His usually perfect uniform was skewed, and his eyes were wide.
"Oh sorry, five" she apologised. Five shrugged
"Have you seen Vanya?" he asked, ignoring her apology. Alison raised an eyebrow, eying her brother. He seemed annoyed and for once in his life, he looked a little lost.
"Why?" she asked. Five snarled
"Why I need her that's why!" he yelled. Allison would have taken a step back but was too amused by the state of Five.
"Are you going to yell at her?" she asked. At this Five looked at her, properly looked at her. He seemed shocked that she would ask that question.
"I would never yell at her; I just need her" he stated. Allison merely frowned
"Then why are you so shaky?" she asked. Five's eyes cleared as he heard her question, he took a deep breath and steadied his hands.
"No… I just need her. She's meant to be helping me, but she has been spending all her time with Klaus" He spat their brothers' name like it was poison on his tongue.
Now Allison was well vested in people emotions. She read enough Teen Vogue to have a general understating of a boys mind. Whilst they technically weren't teenager it didn't stop Allison from realising that going through puberty had a certain side effect. Side effects such as jealousy and possession. Both of which she saw on Five's face. Allison crossed her arms, a smirk appearing on her face.
"My, My Five. Are you Jealous?" she asked. Five's face contorted
"No, why on earth would I be jealous?" he asked.
"Maybe because Vanya isn't spending all her time with you?" she quipped. Five's eyes narrowed.
"Vanya is her own person; she doesn't belong to me. Just because she's mine doesn't mean I control her. She's trying to help Klaus and if you won't help I guess I'll have to look for her myself!" he said before jumping out of the room.
Allison smirked, realising he had called Vanya his. Five was a possessive man, she knew that. Yet never in his life had he defended someone so absolutely and it was in that moment that Allison just knew.