It is unfortunate that Iska seems to have a case of "Dense Harem Protagonist Syndrome," while Alice is obliviously horny for Iska. Despite Iska's condition, out of all of the girls that seem to have romantic interest in Iska, Alice is the one that he seems to be the most consciences about being a close attractive woman in his life, which made the horny Alice's antics to replicate the things that Sisbel did to have a bit more punch to Iska, especially considering he was expecting a more normal interrogation from her, leading both to be left in a horrible state of confusion and embarrassment. If Rin hadn't stepped in when she did I wonder what Alice would have done after pulling Iska's arm deep into her bosom, would they have stayed like that for a while, would they have separated on their own, or would Alice have taken the initiative to do something more intimate than what Sisbel had done?
As it stands Sisbel currently has the advantage of being able to be with Iska more easily because he is acting as her bodyguard, though Alice has had more time to develop a stronger sense of chemistry with him than Sisbel does right now.