Girl Interrputed

In our acting for film classes we have all been given a script and have been put into pairs.
Sav and I are doing a scene from Girl Interrupted 1999. The scene is between Suzanna(Winona Ryder) and Lisa(Angelina Jolie) and is set in a mental institute.
The scene also involves 3 other girls but they are not included and it will just be Sav and I.
We have watched the scene from the film and will watch the full film in our spare time.
The characters are very controversial, Lisa is a socio path who has a massive influence on all the other girls, and Suzanna is a writer who has been admitted to the mental institute by her doctor as she has depression and mixed vodka with aspirin.
We have not decided yet which character to play, as they are both very controversial and complex. Susanna's mental health is questionable as her reasons for being in the mental hospital are quite minor as she was referred by her doctor due to drinking and depression, but the doctor saw this as a suicide attempt, and Susanna had also been having an affair with a married man and became very depressed about this, and after she finished college. She is clearly very troubled but I don't think she belongs in a mental institute.
 But Lisa on the other hand has been diagnosed as a socio path, and from watching this scene I can clearly see she is very mentally unstable and always wants the attention on herself. She is like  a school bully, influencing all the other girls in the scene.The girls are Georgina, Polly and Daisy. 
Playing either characters would be good, as Suzanna is much more level headed and rational, she shows real emotions and is clearly disturbed by Lisa's behaviour. Whereas Lisa is completely mad, she rambles and runs after Suzanna shouting and swearing. Sav and I have read through the script a few times and have been discussing locations for this scene. We want to do it inside, somewhere that looks dark and neglected, there are lots of old unused rooms around the college that we could use for this scene.