Take note of drink size.
The following chart breaks down what equates to a "standard" drink:
Compare these images to what is normally served at dinner or in a bar. How much alcohol is actually in the martini you are drinking out of glass that is twice the size of a martini glass from the '50's? Are you drinking a 12 oz Bud Light bottle or did you order a draft beer? What kind of mug or glass is it served in? Does it hold more than 12 oz? That wine the bartender just poured - think it's only 5 oz or likely more?
Drinkers tend to equate "drinks" with containers. 5 pints of beer? 5 drinks, right? Actually, it's over 6 1/2 beers (16 oz times 5 divided by 12).
While a young woman at Happy Hour may have the best of intentions, the 2 apple martinis she drank are likely closer to 4 martinis.
If you intend to drink alcohol and drive afterwards, take note of how much alcohol you are actually drinking. Get away from the idea of counting the number of containers and focus more on size of the drink.