well...... no.....
It is impossible to prove a negative. I can't prove Pelosi does not have authority.
However, you could study up on the constitution, it isn't very long at all and you would quickly see that the Executive branch holds that power and NOT the Legislative branch...
Article 2 section 2 (in part)
Section 2. The President shall be commander in chief of the Army and Navy of the United States, and of the militia of the several states, when called into the actual service of the United States; he may require the opinion, in writing, of the principal officer in each of the executive departments, upon any subject relating to the duties of their respective offices, and he shall have power to grant reprieves and pardons for offenses against the United States, except in cases of impeachment.
He shall have power, by and with the advice and consent of the Senate, to make treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the advice and consent of the Senate, shall appoint ambassadors, other public ministers and consuls, judges of the Supreme Court, and all other officers of the United States, whose appointments are not herein otherwise provided for, and which shall be established by law: but the Congress may by law vest the appointment of such inferior officers, as they think proper, in the President alone, in the courts of law, or in the heads of departments.
http://www.law.cornell.edu/constitution/constitution.articleii.html#section2
The Logan Act
Title 18 Part I Chapter 45 Section 953:
Any citizen of the United States, wherever he may be, who, without authority of the United States, directly or indirectly commences or carries on any correspondence or intercourse with any foreign government or any officer or agent thereof, with intent to influence the measures or conduct of any foreign government or of any officer or agent thereof, in relation to any disputes or controversies with the United States, or to defeat the measures of the United States, shall be fined under this title or imprisoned not more than three years, or both.
This section shall not abridge the right of a citizen to apply, himself or his agent, to any foreign government or the agents thereof for redress of any injury which he may have sustained from such government or any of its agents or subjects.
http://www4.law.cornell.edu/uscode/html/uscode18/usc_sec_18_00000953----000-.html
Essentially, the only way Pelosi could have "authority" is for the President to give it to her, the white house however strongly objected to her trip.
class dismissed.