I can actually already see the plot going in that direction. Having Iris focus on Kyurem would be alot better than having Ash do it, because of the Dragon/Ice thing. People always complain about how she never works for her development with Dragons or Pokemon, but this time could be entirely different. The ice typing could set her off and make her fear Kyurem, which would mean that it would be far from easy to befriend it. That combined with Kyurem's supposed hostile nature and story would mean that Iris would have to look past everything about her fear of it, as well as others judgement about it.
If Kyurem did kidnap her though, then it would be likely because it would feel that no one else could understand it but Iris. Ash on the other hand would end up bonding with Keldeo, thats almost a given imo.