As King Eomer is aware and has agreed to letting them stay in Rohan I would think he would have informed Athanar of the situation before he left Edoras. the question is how does Athanar feel about having a suspected murderess in Scarburg and the households healer at that.
(even though the charges against her are false, he can't know that for sure as he has not yet met or spoken with her.
) Matrim and Balvir strongly believe she is not guilty and she has already convinced King Eomer and Edowine in previous posts that she is not guilty. I would hope that their would be a few others in the hall that would also stand for her. As Eomer has agreed to Elessar's decree that she be exiled to Scarburg he will have no choice to keep her there, but he doesn't need to like it if you don't want him too. I'm sure many of the origanal mead hall residance will be upset by the deception, as with King Elessar's decree they will have no need to hide who they are.
Like I have said in my post both Balvir and Matrim will lend their swords if asked, but one of them will now always be with Æðelhild probably in shifts, Athanor may want to have his men watch her too but again that is up too you.
I hope to post Matrim and Æðelhild's encounter in the morning (GMT) I would think they would introduce themselves if Athanar does not summon them first.