
Olive Mcbride is a half-decent asset. Her shtick has been mathed into oblivion by better smart guys then I so I wanna add my practical 2-cents to the mix.
A note on the math: Numerical statistics aside, Olive guarantees that you cannot draw a particular token when you don't want to. This means that She's actually great when you're beating the test by +5 or +6 anyway to account for every token in the bag. Think of it this way: The worst token in the bag is , if you're putting lots of power into a test to get to +5/+6 then you can use her to ensure that the doesn't ruin your big swing, you'dd need truly awful luck to pull something like a -4, -5 and an in a single Olly trigger, heck you can even spend extra to account for this particular situation. In short, Olive McBride is good when you do really big skill checks.
Olly is however obviously bad outside her buddy-buddy investigators, namely Jimmy and Mateo. Generally though she isn't all that good for them, Jim's ability does good work even when she's not around and no campaign has enough skulls in the bag to warrant madly pulling tokens out for the fun of it. I'm a bigger fan of her for Father Mateo since she greatly increases the rate at which the shows up and that is good for us, in a pinch you can dig for the too for his 1/scenario ability. For Mateo especially she's good since you can trigger her on the occasional , or treachery that you don't think you're likely to succeed on, either you fail the test anyway or draw an for great profit.
My biggest negative realization about Olive McBride, and the reason I wanted to try her in the first place, is that I figured that she'dd increase my success chance at +-0 with Jim or Mateo, the fact is that she does'nt, all too often i'dd try at +-0 and the first token I drew was just plain 0, only to be followed by some minuses, failing the test. Also, attempting tests with Olly as Mateo at -1 or less, hoping to beat the test with an , is a waste of time, this very much broke the card for me so I've stopped playing it for now.
Second note on the math: Olive McBride has a funny success curve, don't trigger her when you're +1 or +2 over the skill check. Personally I quit using her at +3 (too many 2x(-2)'s!). If you're Jim then +3 or higher is the ideal spot to trigger her to net increased success rate, Mateo should go for +4 before triggering her.
Final note. As a practical note. Olive does interact nicely with Counterspell, Defiance, Hypnotic Gaze, and other stuff that manipulates or interacts with the token bag, but the very very best card in this interaction is Recall the Future. Normally you use Recall the Future to name a token that you can then use Recall the Future to cover, say trying a test at +2 and naming the -3. With Olive McBride you can name the most common token in the bag and draw a bunch of tokens, your chances are now multiplied to find the +2 bonus and game the test ("Oh, I drew a 0, -3 and -4, but I named the 0 with both copies of Recall the Future so I beat the test!"). This tactic is then a good complement to Father Mateos ability and his ability to start with 2 copies of Recall the Future in his deck.