She's a mooch
You're a good friend for buying the first round for everyone, including your buddy's girlfriend Lisa so she feels "in" with his crew. But if Lisa takes that vodka tonic, never offers to get next round, then eats your Buffalo pretzels without asking AGAIN, of course you think Lisa sucks. And the thing is, if she's taking advantage of your niceness, she's probably doing it to her boyfriend/your friend on a much greater scale. Luckily, there are ways to say "No way, bitch" without actually saying "No way, bitch." Next time you go on a Starbucks run and she asks you for a venti skinny caramel mooch-a-lotte, hit her with a, "Sure, you got cash?" Because $9 coffees are actually reserved for women you're sleeping with.
Calling a girl "crazy" is as vague as telling a teenager to be "responsible" -- what does that actually mean? Is Natalie "crazy" because she cries a lot? She could just be in touch with her feelings, which doesn't make her a bad person or lunatic. "Crazy" like she calls your buddy four times a day? Maybe on the DL he likes it (as if he'd ever admit that!) Or "crazy" meaning she threw Domino's cheesy bread sticks at him on his birthday in a fit of vodka-soaked rage? In that case, she's likely crazy... but since the dough wasn't hard enough to hurt him, it's OK to just laugh and thank God you're not the one dating her.