I agree with you. She was smart in terms of protecting herself. She played only the cards she wanted to but not the hand that she was dealt. She was there to tell the whole truth (is that actually in the oath people swear to or is that a tv thing?) and I refused to credit her for cheating at cards. IMO.
If I'm not mistaken, her testimony has nothing to do with MS. Her testimony can only be used against DM and MMs against MS.
Parts of her testimony can be used against MS, like the phone call she claims she had with him and anything she claims to have witnessed directly in terms of his actions or statements.