Just came off a set with a buddy of mine who mains chun…not pretty. He won 2 games for every game I won. She outfootsies, out pokes and outguns gat in almost every facet of the game. Only thing Gat has over her is damage per hit.
IF i were to give 3 pieces of advice, it would be to abuse tigershot at max range and use lots of fakes to encourage a jump in. (oh and if she does jump and u tiger uppercut her, the trade drops gat on his ass so that you can seldom follow up with a step highkick, this sucks, but the damage from the dp is good so…)
Jump in on her while she is downed and go for crouching short mixups into throw.
Condition yourself to uppercut her hazanshou attack (the one where she flips through the air and does a split on your head) its an overhead attack that can lead into kicks ultra if the chun player knows what he is doing. You could also focus attack this move (regular, not ex version) and then punish accordingly.
Crouching jab one links into tigershot or tiger uppercut are helpful (this is a one frame link so it’s gonna be tough but if you can condition yourself to link cr jab 2x into tigershot, it’s effective at keeping her a little at bay.
I know i said 3 pieces of advice, but please, for the love of god…block…block …and block some more till you have an opening. If she has ultra 1 be wary of her charging because it means that she is waiting for a tigershot to give you a fullscreen ultra.
Hope this helps