you go to court to help your friend but you don't arrange your testimony with the intent to help her. your testimony is about telling the truth. and you only testify to what you can remember. you do not say things to give a favorable impression to help your friend. it is not about helping her "win". it is only about telling the truth of what you know. if you are unclear about something, you state that you are unclear, but this is your recollection. if you don't remember, you state that you don't remember. don't try recalling things or piecing together stuff you don't know. it is ok if you cant answer the questions. just say you don't know. if they know you have mental health issues the other side will probably bring that up to discredit you. be honest and state your diagnosis, that you are in treatment?, and that you are stable? that your mental health issues in no way impact your memory or your ability to be honest or testify. going to court is anxiety provoking. I usually take a klonopin before I get on the stand....just review all the facts that you know about the case so you are very clear about them before you go in. don't deviate from testifying about anything but those facts. you cant testify about something you don't know..they like to ask you to presume things. don't let them only talk about the facts that you know....good luck.