Mary truly didn't want to help Vanessa, but realizing how badly she can screw up on a simple task, she bet that she would continue to make the situation worse.
If Mary continued to reject her, and Vanessa went to Theobold for help, she would definitely expose her suggestion, then things would turn bad.
After all, Theobold had just discovered a traitor among his precious military team.
So if he found out that Mary also attempted to leak information to create a diversion and easier situation for her. Then the chances of Theobold using her as the sacrificial lamb were high.
And there was no way Mary would allow herself to become some sacrificial lamb.
"Ugh, just get inside the Iron Sentinel, but remember this. Whatever you see inside, you better keep quiet about it and not expose it." Mary stepped closer to Vanessa and warned solemnly.