My thinking is to let them work things out. If Boo seems willing to make amends and the agression IS getting better, I think them working things through will be the best thing. Does Boo have a problem with being isolated? Take this into concideration as Ive seen cats go balistic being isolated. Id think its better just to let things happen between the cats rather than potentially undo quite a bit of good progress.

Hope thats somewhat helpful