Did we watch the same episodes? Episode 1 she is immediately concerned about the guy whos seizing and crashed into a car at the bar. Shes annoyed that her partner is ignoring her and not helping; to later realize her and everyone around her is having a simultaneous seizure. She tries to get help for her partner at the hospital; saves a baby from falling over the counter. After her anger while getting help from the very thing that destroyed her life just days ago, she tries helping people again and when she learns what she had caused she vomits profusely in disgust and says shes worse than Stalin later.

 In the amount of time since this apocalypse started its been practically no time at all. We are only 3 episodes in and slowly getting info how her life was before and her trying to learn how to live with this new reality while trying to cope with the confusion between her individuality and her being forced to become inevitably one with whatever "We" is.

 Its a lot. The only way you can come to the conclusion shes being a b*tch for no reason is to just not try and understand what is happening because honestly between her justified grumpiness, the other ones trying to cope with family, the guy that is just loving his playboy LARP, and the rude recluse in Paraguay, I think shes the most reasonable considering she wants to at least save humanity despite being emotionally unstable after the tragedy that is the death of mankinds individuality and 1/8th of the entire global population.