No worries
Even assuming Narcissa's Drifblim has a nature favorable to speed (which I doubt), a 31 speed IV, and has 252 points in its speed EV (which I also doubt), its speed stat comes in at 94, well below my Crobat's 125 (his nature is neutral for the speed stat and his speed IV is 20). Drifblim's base speed stat is simply too low, it's impossible for it to be faster than my Crobat without something like Trick Room being in effect, and it's certainly not; I also don't see anything that would affect his speed in the field effect manual.
Edit: What is her Drifblim's ability? I can't find it documented anywhere, the wiki doesn't have her teams right. I assumed it was Flare Boost considering it burns itself, but I suppose if it's Unburden and there is for some reason no indication in battle when Unburden is activated, my confusion would be resolved.