Beth notices that Baltasar is wearing a name badge in Spanish. She tries to trick by asking him in Spanish if he's from Spain. He answers back in Spanish that he's from Argentina. However, his purported Argentine accent is so bad that Beth would never have believed it (since she speaks fluent Spanish and lived in South America), but she does and walks away, seemingly convinced.
The complex plot to assassinate the President on the steps of the hotel is supposed to be a smoke-screen for Anna's real plan for blowing up herself and the President at the Peace Talks. However, if she had simply used her "injected explosives" plan without raising the alarm with all the other business then she would in all likelihood have succeeded.