Continuity mistake: When the Scoleri Brothers come (for whatever reason) out of the jar there are strong air currents all over the courtroom. The heroes are under the table, and you can see the winds knock down a few books above them. In the reaction shot on the crowd after Ray goes "Wooooow", you can see some of those books that just fell earlier still on the table. Look for instance at the two books by the red tome to the far left. (00:32:40)
Continuity mistake: The smaller Scoleri tosses the defense table at the judge's empty podium. In that sequence there are no burning fires (a tiny one quickly fades) and not even the glowing jar of slime. When the Ghostbusters arm up, the slime is smoking and glowing and fires burn at the judicial bench. (00:33:05)
Continuity mistake: After "Do, Re, Egon", the Ghostbusters are nervously waiting for the Scoleri to show up, as if they knew they would. Just before the camera cuts to a close-up on Bill Murray, he begins to lower his head to look at his rifle, but in the close-up he is facing forward. (00:34:40)
Continuity mistake: When Egon sucks the Scoleris inside the trap, the three 'busters are spread across the courtroom, but in the close-up of the trap you see their legs being much closer - and you can see for instance by Peter's stance that there's no real continuity. (00:36:20)
Continuity mistake: When the ghostbusters are yelling at the jar filled with plasma, on the close-up Venkman's hand is around a metal thing, but on the wide angles it is just by its side. This keeps changing back and forth. (00:39:20)
Continuity mistake: When Ray screams at the slime that "YooOOOuuUUU take the cake" his wrists in the background are crossed and the watch is visible. Cut, and his hands are joined and the wristwatch concealed. (00:39:45)
Continuity mistake: During the dancing toaster scene, the pool balls' position differ depending on if the wide or close angle focuses. (00:41:25)
Continuity mistake: Peter drops by the museum to see Dana. As he enters room 304, a worker there is wheeling away a big crate. Cut, and the crate spun 90° (just check the stickers and the "Keep dry" writing, first on the right side, then on the side facing the worker). (00:42:40)
Continuity mistake: Janosz interrupts Dana and Peter talking about the Gaugain; behind him there are a man and an elderly lady passing by. Cut to Sigourney Weaver, and in the next shot the two people practically haven't moved. (00:43:10)
Continuity mistake: Dana and Venkman watch the painting for the first time while Janosz climbs a ladder. His hand swaps between grabbing the railing or raised, between shots. (00:43:45)
Continuity mistake: When Dana tells Peter that she thinks the painting is watching her, Peter turns towards Vigo with the whole body. In the close-up, he's glancing at the painting sideways facing Sigourney Weaver. (00:44:25)
Continuity mistake: While Dana is cleaning her baby for the bath, the bottle and sponge next to him move around between shots, the tissue popping out appears/disappears randomly, as does a towel on the corner. (00:45:20)
Continuity mistake: The pink slime in Dana's tub grows up to a height of 6 feet. then a frame later it's really small and it's growing-up again. (00:45:45)
Continuity mistake: The floating toys on the stool by Dana's tub disappear when the water becomes pink goo. (00:45:50)
Continuity mistake: When Dana and Oscar are at Venkman's place right after the scene where the bathtub attacks them, there is a slight mistake. Dana is shown from her left side, and she is holding Oscar. Oscar turns his head towards the camera, and almost immediately the view changes, and Dana is shown from her right side. Only thing wrong is that Oscar is still looking at the camera without ever turning his head. (00:46:15)
Continuity mistake: When Stantz and Egon watch the computer encyclopaedia, in the close-ups the information shows up in several single lines, but in two big paragraphs in the wide angles. (00:47:30)
Continuity mistake: While Egon and Stantz check out the computer screen, the books on the right change positions between shots. (00:47:30)
Continuity mistake: Peter leaps on his own bed after telling Dana that she can treat his house as her own. Between shots, the spare clothes tucked under the covers and those lying on the box by the window change entirely. (00:48:45)
Continuity mistake: When Ray passes the paper with Vigo's biography to Peter outside the museum, the passers-by change at the cut. (00:50:00)
Continuity mistake: In the scene where the Ghostbusters arrive at the museum, and Egon tells Peter what he's found about Vigo, while speaking to each other Peter gets a bag and hangs it around his neck. In the shot where you only see Peter's back you can easily see the strap hanging straight down. But in the shot where Peter's face is visible, he's holding up the strap with his hand quite high. Cutting back to Peter's back the strap is hanging straight down again. (00:50:20)
Answer: Because she knew Peter would want to get involved. They didn't part on good terms and she hadn't spoken to him since her marriage. She just thought it would be awkward to see him again.
Bishop73