As far as the love triangle dynamic goes, I suppose Tara/Willow/Oz is a pretty good comparison to Lauren/Bo/Dyson. (Although, I'd say Dyson still has an outside chance, whereas Oz never really did.) Would that mean Tamsin is Kennedy then?
But as far as how well Lauren integrates with the rest of the group, I stand by my Riley comparison. (As much as I liked him, he never fit either.) At her best, maybe she's like Cordelia or Anya. (Decent characters that wouldn't really be spending time with any of the rest of the group if she wasn't dating one of them.)