We don't know about her reason yet but some ppl are saying that she was pregnant with her co star and something happened
I feel people may just be wanting to dramatise this by throwing murder accusations etc, but it could also just simply be that there was something going on with her mentally/ emotionally and her co-stars vanity was the most convenient place she found somehow in that she found the means she needed in that room. Disturbing that people are dramatising it and might target her co-star unnecessarily before things have been full investigated.