@hanna is a lawyer. Harvard law school. You are right that she does not represent her clients in courts of law, but within the framework set up by universities in title ix proceedings, and also advises those who want or have to transfer in where to go and how best to apply there.
But that is neither here nor there because it she does not appear to be active any more on CC and it is the OPs decision whom to hire to help her son navigate this.
Those who insist that “those girl(s) must be stopped!” must always remember that, whether the young woman who has publicly accused OP’s son of assault is mentally unstable and vicious or genuinely traumatised by how she experienced the relationship and the breakup (all, or none, or some of the above may be true) the one inescapable fact remains that she has done so, and may do so again, in an environment where someone is a mandated reporter and the disciplinary juggernaut starts from there. We still do not know whether there were sober, credible witnesses to the one altercation OPs son admits to have happened, and no one here, possibly not even the two protagonists, can know at this point whether verbal assault and threats can be construed from what has happened, but the risk remains.