Katja wont open up to you unless you have good grades, decent make up skills, little or no slut rep and decent attractiveness rating on top of the 60+ relationship requirements.
That's at least more concreate then what I started with... The wiki and FAQ just say 'get drunk at the disco'.
Attractiveness should be fine at 150-170 (& 7-8/10). I'm usually in the top 3 hottest girls in school. xD
And I have no 'slut rep' currently... Thankfully, since the tracking is a bit weird and thinks I've only slept with 1 woman and 12 guys...
Also my relationship with her is sitting at 100... I may have spent a lot of time talking with her at school even though she mostly ignored me. I'm actually surprised I'm only 'tolerated' by the cool kids as only Dimka, Andrew, Mefodiy are still at 30 with me. Everyone else is over 70. xD
Is 33 Makeup 'good'? I mean that's up near my highest skills currently...
My grades may be holding me back as they are all 3's (61-63)...
Vicky I dont know much about other than going to the park and walking around until you see her and Vanya enough times for her to invite you somewhere. They should both have journal entries under quests section that could help.
Eventually she finally popped off! One day leaving school she just dragged me to the cafe (not quite 'invite' of the wiki). Though the beach step I did accidentally. I went to get a tan on the beach and ran into them, no previous invite so I'm not sure how you'd know to go there. A bit awkward for me though as Aunt Luda's partner Olu had just go to town on me the day before and I was still sore from that. xD