A few years before becoming the Vikki you all know, she had gone through a difficult period, after losing a close friend who accompanied her and her friends on their space adventure and the group dissolved after this tragedy.
On her return to earth, she returned to the former laboratory of these deceased parents to make her home there and sank into a deep depression.
Having no family, these friends went to each of their corners after the tragedy and not knowing what to do with her life, she spent the majority of these days doing nothing except eating, watching anime and playing video games.
This resulted in her gaining enormous weight, until she couldn't have enough energy to get up. Fortunately, she has reprogrammed one of the robots in her room that she made during her childhood, so that the robot can take care of feeding her, washing her and lifting her, if she has to be lifted.
This period was difficult for Vikki, until considered useless during these worst moments. It lasted more than a year, before her got out of it, having found a purpose in her life.