We don’t have a ton of details here, but I think suicide is unlikely. I see foul play as being even more unlikely than that.
She was exhibiting strange behavior, and taking the words of her family and friends at face value, that was highly unusual.
Having some sort of a sudden onset mental health episode is reasonable, but that doesn’t explain her suddenly dying from such a thing.
So I’ve got to think that she had to have consumed something that caused her death (the weather doesn’t seem conducive to exposure).