Ever since Nicola’s disappearance, police had insisted that their main theory was she went into the river although they still had two other, less likely, hypotheses: that there was a third party involved, or that she left the area voluntarily.
Article source: https://www.huffingtonpost.co.uk/entry/nicola-bulley-body-found_uk_63f35f27e4b0616708dc98a9