Run through "Siege Shield" to deny Ash’s zoning. When shield is behind you, its no longer useful for Ash & her team. Be careful and don't do that trick on low health - Ash might burst you down.
Ash is super annoying to deal with. Her damage output is surprisingly high for a tank, but only at close range(unless they have slug shot). pick her off from a distance if at all possible. if not then wait for backup, you Will need it.