I think the truth is nobody knows what Libby's state of mind was that night.
Her flat mates were obviously concerned enough that in a very short time from her not arriving home they were searching for her and the police were called so to me that hints that they had high level of concern about her safety and most people wouldnt automatically assume a 3rd party involvement within such a short time either. Maybe the concerns were just about the weather and her having had too much to drink but we cant know that.
However I dont think she committed suicide, no way. No matter how traumatised she was after the rape (if she was still alive which I dont think she was) I dont see her making her way to the river and throwing herself in.
It is upsetting that her mental health was scrutinised so much by the defence but on reflection I can see they had a job to do no matter how harsh it sounded but I personally dont feel it had any relevance other than she was in a distressed state and someone that could have helped her did the exact opposite and is responsible for her death.