I would be guided by the evidence which shows me her activities showed purpose and planning in spite of everything, preparing clothes and showering, nothing had changed in her life between Mary's call and Nina's text, and her dropped towel and missing sanitary protection is more indicative of a shocking intrusion at the entrance to the room than a change in mood.
For the poster above to be correct, the drastic slip from "helping" to suicide would have had to happen prior to NR's text, prior to JS's call, prior him leaving the "devastating message" and prior to anyone having retrieved the same. Hmmm... Doesn't quite work.