Mainly when going up against Skye, you'll be already halfway below health because she has surprised you. In that case use Withdrawal to counter. If you feel like you're ready, or Skye is about to disappear, use Planted to shred her 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.