And the Sky Full of Stars - S1-E9
Revealing mistake: Inside Sinclair's mind, just after the knight shoots the fake Garibaldi, he lowers his gun and the end briefly lights up red. Evidently the actor accidentally pulled the trigger on the prop and triggered the light that lets the CGI team time the effects correctly. Note that it is not the gun barrel glowing after shooting, as it is not lit up before he lowers it.
Chosen answer: She was promoted to Captain and thus had to leave Babylon 5, becoming a captain on a new Warlock class ship. Later on she retires/quits and becomes the top Ranger on Minbar.