I will agree with Shambala108. The text does not say that it is Tbor who is beating Kilara. The fact that is that there are bruises, and Kilara hides them from Tbor.
In my opinion, the phrase is constructed in such a way as to say that the bruises were left by passionate Meron and Kilara hides them as a sign of treason, but if Tbor tries to accuse her of treason, then she can say that he himself beats her when he drinks ... Thus, they maintain mutual parity. Tbor does ignore the treason, Kilara does not spoil Tbor's reputation.