Really? And when does that happen?
In the Haunted House, you are supposed to hide (click text or hit spacebar) when she gets close. Though when she catches you get a couple of bonus CGs so worth getting caught at least once. To get the Vampire Spit keep the light on Astrid until the bar fills up. You need to do this 3 times and after this the Vampire will show up when you return to your room. NOTE - You do not actually get Vampire Spit here I think it is a visual bug, you get it on the 4th time of completing the Haunted House.
Regardless on the 3rd completion of the Haunted House, you can then tell Emma about Astrid in the district on Tuesday, you then need to enter the Petrol Station