As
OvaLoaf mentioned before, Tess's cosplay event is RNG, but there's a way to tell if it's going to happen in this hunt.
Basically, the closet that exists in parents' room is where the MC can hide.
However, as shown in the image attached below, you can see that "hide" has been changed to "talk" with a certain probability, and when you interact, the MC says that the closet is locked and you can't hide.
If you see that parents' closet is locked, you'll see 100% of Tess's cosplay event when you catch a ghost. (Talk to Tess, who is having sex with Mac, and you'll see why it was locked.)
Of course, if you want to see this event, you have to recruit her from Evergreen University first.