Would totally make sense if it was at all consistent with her previous reactions. Jean's been a senior x-man for years, but generally reacts extremely emotionally to losing anyone. When it's someone close to her, her reactions tend to be over the top.
Here's one from just a few years ago from Jean's POV
Actually the reaction you described is exactly how I would expect Scott to react, but definitely not Jean. Look, we could easily chalk it up to a number of mundane explanations. It's just the timing of Charles screwing with Jean's emotions that made me think along these lines.
Also, conspiracies are what we do around here