Okay everybody, on my break I stood outside and thought about a solution that might work for everybody. And yes Thorin and Rochey I am taking your position into account.
The problem is, we have two headstrong people who do NOT get along, apparently IC or OOC, who basically want access to some of the same privileges and character decisions. Thorin is Tactical Officer which includes the fighters, Blackstar wants to fly and to have some fighters at hir disposal.
So here's what I thought up.
Blackstar has an intelligence background... perfect. So keep Thorin as the ship's tactical officer, but Blackstar's new role could be an attache from Starfleet Security. Hir higher rank fits in perfectly with this. Basically, in all normal and routine operations, Thorin is the ship's tactical officer. But in specific situations (say particularly in regard to the Tholians, or some specific sort of threat or mission profile) Blackstar has the authority to commandeer and use specific assets (namely the fighters or shuttles) to accomplish certain mission goals. And yes, this is a source of sometimes friction between the two characters, and you can work that into the RP.
There's a lot of Sci Fi precedent for this. When Sisko was gone, Kira was in command, but Worf tried to overrule her command that no leaves the station by citing that he was commander of the Defiant, and might have the authority do it against her say-so. Eddington and that other guy coming in as "Starfleet Security" representatives overlapped duties with Odo and sometimes took precedence as the senior decisionmaker in situations involving greater Starfleet security, but not in normal routine security or station tactical issues. For instance when a ship pulls up that's a station issue but if the Maquis attack a Federation freighter a short distance from DS9, that was a Starfleet Security issue. In Battlestar Galactica, the sudden appearance of the Battlestar Pegasus and Admiral Cain. Some main fighters were trasnferred to work under the Pegasus's command, and Adama had to defer some issues to Cain's higher rank-- though of course this created friction in many instances. The struggle between President Roslin and Commander Adama in issues of whether a specific case was a civilian issue or a military issue could also be used as a template for story ideas.
So Blackstar would not "take over tactical', nor would she shove Thorin aside and say "I'm doing torpedoes today." But in specific story instances she would have authority to, say for example, inform the captain that she needs the use of 4 fighters for x mission for recon or for a special Starfleet op. It would be up to the captain, not Thorin, to make the judgment call on whether or not the ship can spare the resources, though of course if he refuses without ample grounds he might get a call from Starfleet.
I think this would preserve Thorin's role, while creating a role Blackstar would like, while simultaneously reflecting the rank difference. What does everyone think?