I really don't understand how people can say charla used dave. Charla COULD have used dave easily, but instead went above and beyond the call of duty IMO to make it clear to him that she DIDN'T care for him beyond a simple game partnership. She had also done this at times when he COULD have screwed her over. I think that showed great character on her part. Quite the opposite of what many of you apparently see, I saw that she was NOT going to feign interest in him in order to stay the game. She made it clear EVERY time it became a topic of interest that she DIDN'T have intimate feelings for him. And can a SINGLE one of you say that Dave didn't "use" Charla? No you can't. Not honestly at least. Dave knew for a fact he had NOWHERE else to go. To say he wasn't "using" her is to be disengenuous at best.
This is why, if you will watch the show honestly, Dave was always questioning her loyalty. HE WAS USING HER, not the other way around. She'd never given him a single reason to question her honor, but he did so constantly. She made a promise, yes she did (pinky swear), and SHE KEPT THAT PROMISE. If you disagree, kindly show where she broke her promise to him.