The red tape in the last episode? Spoiler.
When they are about to have the party nearing the end of the last episode, Tina makes sure to tell a couple of the girls to be careful as the contractor hasn't finished the railings upstairs yet. Bette then quickly mentions that "there's just red tape up there now" before they move up the stairs. Jenny is not present in this scene.
In the scene where Bette confronts Jenny outside you clearly see the red tape running around the balcony. The fact that they made an effort to point that out kinda makes me believe it was an accident. Maybe after the confrontation Bette walked back inside and Jenny turned around, not realising there was no railing and she fell into the pool, hit her head and died?
At least I'd like to believe this is what happened as I don't really see any of the other girls as capable of murder. Maybe Bette pushed her... but she seemed so collected and calm during their last conversation. Considering how angry she's been before on the show and she never got violent I really don't see the sense in it.
Anyways, interesting ending. I loved the show. I'm as straigh as they come but I'd still give Shane a go. Cough.