The first was Stephan, not noticing anything strange about her until the moment she took action.
Her acting was the most crucial for making that part a success, along with being able to respond to whatever was happening to keep herself safe and not let her act slip as she would try to maintain her lies for as long as possible.
The second was ensuring that Stephan did not call Gerald, even though she had stated that she wished to meet with him.
Having one extra person to deal with or an extra person arriving unexpectedly would always increase the difficulty of being able to succeed.
The third was taking note of the surrounding threats that existed all around her and what could be used to her advantage.
She was in an unfamiliar space that Stephan was far more familiar with, so he held the advantage.
