*UPDATE* I've noticed a lot of comments inquiring why they didn't have a threesome (which would've been awesome, I agree) but that's kinda the whole point. Ariel was clearly enjoying Ursula's projections of Al and Jas fighting, while her deal was to separate them (she didn't know it would KILL them). She is supposed to be a terrible person. Ariel is so selfish, that she wants them both to herself and not for each other, and her selfishness is her outdoing. Ariel deliberately tries to get between them, she's not oblivious to the fact they both desire her, or to even her own actions, and that is ultimately the death of them and her own heart.

This was fun and I'm actually proud of this! :D
Plot; Ariel sees Aladdin and Jas and instantly falls in love with both of them [Hey shit happens] However, they are already happily together, so she visits Ursula who tells her that if she becomes human, Aladdin and Jasmine will be separated.
The one thing Ariel doesn't know, though, is the only way to separate them is through death. That and Ursula is just a major biatch.