Standard Deviation....of Blackjack?

[LondonBroil]

Non-poker related post.

I decided to post this after returning from a trip to Vegas where I had 2 killer blackjack sessions. I don't play too often but the last 3 times I've gone to A.C. I've come out a descent winner (30~40x my bet) with maybe 3-4 hours of playing. I know the game is supposedly -EV in the long run, but I've memorized the standard strategy and use a basic counting strategy (I've always been extremely proficient in basic mathematics being able to add, subtract, multiply, and divide numbers very quickly) so maybe I can beat it?

Basically, whenever my g/f and I go to A.C., she ALWAYS loses, mostly because she doesn't always do what your "supposed" to do. She likes staying on 16, she doesn't always double on 11, etc.

If I gave her the basic card sheet, and she memorized it, it cuts the casino advantage to around 2.6% (I think). Is there a way to figure out a Standard Deviation per x number of hands played, say 100 hands?