Frocking customs and policies vary across military services, particularly for enlisted members; in the United States Army a general officer may request authority to frock soldiers of his command; in the United States Air Force, only senior field grade and general officers are usually frocked.
The United States Navy makes use of frocking much more frequently than do the Army and the Air Force.
News of the promotion of an officer arrived, usually via letters brought by another ship, and often with orders for the newly promoted officer to report to a new ship or station.
The ship that brought the news would often take that officer away to his new post.
The acts and circumstances must be such as to lead a reasonable person experienced in the problems of military leadership to conclude that the good order and discipline of the armed forces has been prejudiced by their tendency to compromise the respect of enlisted persons for the professionalism, integrity, and obligations of an officer. Regulations, directives, and orders may also govern conduct between officer and enlisted personnel on both a service-wide and a local basis.
Relationships between enlisted persons of different ranks, or between officers of different ranks may be similarly covered.
I'm almost certain that my BN CO (who I've served with before and knows me much better) is aware of her status but has not said anything to me. If you are concerned about UCMJ liability there is probably none.
(1) She is not a US Officer and (2) fraternization only applies to Officer (on their end).
For officers in the same rank or paygrade, seniority is determined by the date of whom assumed their rank earlier.
The gist of this offense is a violation of the custom of the armed forces against fraternization.
Not all contact or association between officers and enlisted persons is an offense.
In the United States military, frocking is the practice of a commissioned or non-commissioned officer selected for promotion wearing the insignia of the higher grade before the official date of promotion (the "date of rank").
An officer who has been selected for promotion may be authorized to "frock" to the next grade.