Crazy good.
This card is a Sneak Attack on tap, it gets expensive to run but sure enough but with a relatively basic resource generation engine you can trigger her most rounds. Typically evade values are a bit lower than fight values and the vast majority of threats have an evade value of 2 or 3. A card like Lone Wolf will make you just enough resources to be triggering Delilah O'Rourke repeatedly.
To get the most from Delilah O'Rourke you need to be evading, not a problem for high characters like Finn, "Skids" O'Toole or Winifred Habbamock. Finn Edwards in particular with his free roundly evade can kill a minor enemy before he even spends an action! Even if you dont evade though, nailing something with an automatic 1 damage can be so very very helpful, say for example to put a point of damage on an odd-health opponent, also dont forget that there are several 1-health enemies that an angry Delilah O'Rourke will make short work of!
Oh, right, did you notice that she also buffs two stats and has some tank? What IS this crazy value?! Fighting with tends to be expensive, so there's a little anti synergy with her ability, a cheap combat method like Switchblade or Sleight of Hand + Lupara or other inexpensive weapons is recomended (like .18 Derringer for Finn, Enchanted Blade for "Skids").
Between Lola Santiago and Delilah O'Rourke characters sure are spoilt for choice.