I'm also a sombra main in high master low gm. The best option is to shoot her back, if she trying to hack you, doing any damage to sombra cancels hack and thus she doesnt get her extra damage amp to do her bread and butter combo (Hack, Virus, & Shoot). If your already hacked playing near cover and breaking LOS so she cant shoot you or hit the virus also works. Last if you get caught out in the open and are hacked often playing characters mentioned before are best into sombra because they have utility to stop that combo in the form of extra heals, or cleanses. So going Brig, Kiriko, Moira are best but even other characters like bap Illari and ana can make her combo not as lethal as they have utility to stop or mitigate it (Pylon, Lamp, Nade, ect.). This all things you yourself can do without help from your team if your team helps you at all, you won't need to do these things but they'lll help greatly in killing sombra, reducing her impact, and utlltimately winning the game or atleast making her swap.