I doubt its a stun, there's no way they'd make a ranged flashbang after everyone called for mcree nerfs.
Also I feel like she has a climb of some sort, but I might be thinking that just because she was on top of the gate in the beginning

ツ

IcyWind#11662
best tracer in my neighborhood

I haven't played comp tf2 in almost a year a now, and after like 6 years I think its time I finally move on