Kelly did say “last to join, first to get eaten”, which implies that she did in fact ‘join’ the Marra, and she was seen consuming the green energy alongside the others. She may be an inexperienced novice, but with practice, she could potentially do things like turn into mist, fly, and even influence people’s dreams.

Maybe she could use these powers for good, like giving people positive dreams, or hanging out with her friends after they’ve gone to bed (although her parents might disagree with that being ‘good’). And flying/turning into mist would certainly be useful on adventures.

Although, on the downside, she would never be able to wear a leather belt again.