I feel it may be relevant to this thread that the Equalities Act came into existence in 2010. That act placed far higher emphasis on harassment and bullying, especially in workplace situations. Many employers and other organisations carried out investigation reviews to ensure their grievance and disciplinary procedures complied with the new act.
As this allegation seems to have arisen at the time when the Labour party may have been reviewing their harassment and bullying procedures in regard to the act, it may have been that the matter was brought forward as part of that review.
However, should the above be the case then immediately Bex Bailey made the rape allegations to any member(s) of the review team, then the matter should have been placed in the hands of the police or those hearing the accusation would run the risk of being accused of perverting the course of justice.
If Bex Bailey had only spoken on the matter in the course of the review rather than making a formal written allegation statement to those empowered to deal with such issues within the Labour party, then that may give some reasoning why (if it is indeed the case) Bailey was given the advice she received.
The above stated, it still leaves why whoever heard the allegation in the first instance did not immediately contact the police. I believe anyone experienced in hearing harassment and bullying accusations would have informed Bex Bailey on hearing the allegation that the matter had to be placed in police hands as she had at that point involved a third person in what is a very serious crime allegation.
Just my thoughts?