She's expensive(212k cap hit this season) and she doesn't really fit into the future of what the Fever are going to be. Fever are not going to be an isolation team as long as Clark is there, they're going to be a screening, cutting, ball movement team if they get a coach who knows how to run an offense.
As for Kelsey, she's a good shooter that is lightning quick and brings good energy. But is also a ball hog on offense and short plus not good on defense. Those problems don't pair well with Clark in the guard court.
She's not going to be a backup, so I don't expect her to sign with Indiana. What will be interesting to see is what teams out there wanted her. Indiana, being a poorly ran franchise, had to overpay to keep her after her rookie contract. Other, better ran, franchises won't offer that much money for a player that isn't good at defense and barely passes the ball.
With Wheeler coming off the books at the end of the season, if they let Mitchell go too that frees up a huge amount of money(>400k) to go after free agents. They might have to overpay on someone, but they could bring in a 3rd star to pair with Clark and Boston. I'm thinking an SG that can play defense or a defensive big that can play next to Boston. And then look for a veteran PG that can play backup minutes to give Clark some more rest.