(This Contains Spoilers for Episode 2! You have been warned!)
So towards the end of episode 2 you are presented with the dilemma, where the bullying and harassment has driven Kate Marsh to try and commit suicide. She is going to jump off the top of the dormitory clock tower. Max manages to use her powers to pause time to reach the top of the tower just before she jumps. However, in pausing time she used up a lot of her powers and couldn't rewind anymore in that particular moment. You now to select the right answers to save Kate's life and there are no second chances in this particular moment.
This is possibly one of the most pressured moments in the entire game so far due to that is the first, and only moment, in the episodes that make you deal with your consciences and choices in one moment instead of later. In other words, instead of your choices coming back to bite you later, they actually bite you in the here and now.
So, while you are on the roof Kate will bring up a few moments in the past that caused Kate distress and cause her situation to worsen. For example, whether you stood up to David or not and when she asks you about whether to go to the police. Most of the things you need to know and do are found in the girls dorm.
First, do all the erasing on Kate's slate outside her room and the web link to her video in the girls bathroom on the mirror. This gives Max something to show to Kate as proof that she cares. When you are in Kate's room giving back the copy of the 'October Country' have a look through her things in the room. Near the rabbit cadge, there is a postcard from Kate's father. It says how he cares deeply for her still and quotes the bible about having a light at the end of the tunnel. Further along on in her room their is a letter from her auntie. It is not a good letter. She shames her in the letter and says that Kate should "Pray for forgiveness." This means that when it comes to the part for saving Kate you will be given the option as to who will miss her if she follows through with the suicide. Choose her father because she refers to the postcard and brings you one step closer to stopping her from jumping.
Finally, you must mention gathering proof and hunting down Nathan Prescott's involvement in drugging her. Every chance you get to benefit Kate in your choices, make that choice if you want the best chance in saving her. You don't have to do everything that benefits toward Kate to save her, but by making all the choices benefit Kate, you have a much better chance in stopping her from jumping.
So those are the main points on how to save Kate Marsh. Hope you enjoyed and hope this helps.
Happy Gaming!