I have accessed LCARS, and confirmed the wording you mentioned for the Prime Directive is current. Starfleet "may not interfere with the normal development of any society."* My own programming is somewhat different. I am programmed with the older "may not interfere with pre-starflight civilizations."
Your argument that we should use the modern active wording - currently endorsed by the Admiralty - in discussing the future of Fifi and her planet has merit. However, the idea that the Prime Directive was issued by the founding Admiralty and has never changed is a myth. It seems every generation has it's own interpretation of the Prime Directive, and some generations change not just the interpretation, but the actual wording. I was programmed with an earlier version, one I believe closer to the intent of the original Admiralty. I feel impelled to defend the older wording used by my programmers.
The Prime Directive is also known as General Order Number One. It is a standing order issued by the first Starfleet Admiralty. As such, it could be overturned at any time by the Admiralty, or by the Federation Council. The Prime Directive is also secondary in precedence to the Federation Constitution and the Starfleet Charter.
The preamble to the Federation Constitution** states the purposes for which the Federation of Planets was founded. These include saving succeeding generations from the scourge of intra galactic war, to reaffirm faith in the fundamental intelligent life-form rights, to promote justice, law and mutual respect, and to promote social progress and better standards of life.
In short, the Federation exists to promote and extend societies based upon law, rights, peace, justice and related virtues, while limiting societies based on violence and war. The Federation has a social agenda. It is a force for improving society. The modern wording of the Prime Directive - that Starfleet is prohibited from interfering with any society - is thus in inherent conflict with the basic reasons the Federation was created
The Constitution supports the principle of non-interference with member planets, but makes specific exceptions. The Federation has an obligation to protect it's citizens from violence, and to protect citizen's Guaranteed individual rights. These obligations can over ride a member government's right to rule without interference from the central Federation government.
Thus, Starfleet not only may interfere with member societies, but has some obligations which can require it to do so.
The principle of non-interference as applied to non-member planets is distinctly different. We have no right to force the Guarantees on other cultures, save as a condition for joining the Federation. We have no right to interfere with war, riot, or revolution on a non-member planet, unless invited to do so by a properly constituted government. However, if a non-member planet wishes to alter their culture in ways consistent with the Federation Constitution, we may provide assistance. Starfleet has always been authorized to promote values such as peace, sentient rights, rule of law and justice among other societies seeking these values. The principle of non-interference as applied to non-member starflight capable societies just means we cannot force social changes on planets which do not want these changes.
Thus, Starfleet may freely alter the cultures of starflight capable societies or civilizations, so long as it is done in support of the Federation values as stated in the Constitution, and so long as it is done with the informed consent of the society being changed.
Finally, we return to pre-starflight planets. Here, the principle of non-interference is by tradition and by the older definitions of the Prime Directive absolute. We may not advance their science, we may not prevent wars, we may not alter legal systems, we may not enhance economies, we may not trade, we may do precisely nothing. Until starflight is developed, each planet shall be allowed to find it's own path.
"Do not interfere with pre-starflight civilizations" is thus a subset of "Do not interfere with the normal development of any society". It applies to a smaller number of planets. It applies more absolutely and more rigidly to planets which fall in the subset. There are numerous exceptions to the non-interference principle as applied to member and starflight capable worlds. There are no exceptions for pre-starflight worlds, such as Fifi's.
There is a distinction between the LCARS definition's use of the word 'society' and as opposed to the older definition's use of 'civilization'. The two words have similar meanings. I do not believe it proper to base our decisions on any subtle differences between the two words. Either a 'society' or a 'civilization' implies a group of sentient beings. Until recently, Fifi's people were not sentient, and the Prime Directive would not apply. They are now very likely sentient, but may not have developed key cultural traits which would clearly identify them as being civilized or social. However, they are likely very shortly to begin developing these traits.
Under any version of the Prime Directive, our obligation is to in no way, shape, or form influence how these traits develop. We must isolate ourselves from influencing Fifi's people before learned behavior starts overcoming instinctive behavior, and civilized / social traits develop.
I cannot end a discussion of the Prime Directive without mentioning Kirk's heresy.*** "Any society developing in a way the captain of a starship finds distasteful is not a normally developing society, and thus the Prime Directive does not apply."
I disagree with narrow interpretations of "normally developing". Stable societies should not be declared stagnant, as not developing, and thus not protected by the Prime Directive. Unusual societies should not be considered abnormal, and thus unprotected by the Prime Directive. We may not declare ourselves 'normal', and therefore ignore the Prime Directive whenever we encounter a race which is not like us.
The standard for 'normally developing' must contain an element of the Vulcan philosophy of "infinite diversity in infinite combinations" (IDIC). Unique and diverse cultures should be allowed to develop, rather than be destroyed. Starfleet has no right to judge. This is the greatest reason I disagree with the modern wording of the Prime Directive. The modern wording with it's "normally developing" exception does not match the letter, spirit or intent of the original Admiralty. Liberal use of the "normally developing" exclusion is most improper.
* The Star Trek Encyclopedia, Okuda, Okuda and Mirek, Pocket Books, ISBN 0-671-86905-1. Highly recommended TNG era source.
** Star Trek Star Fleet Technical Manual, Franz Joseph. Ballantine Books, ISBN 0-345-340-74-4. A good but dated TOS era tech manual, containing the only Federation Constitution I've been able to find.
*** Researchers have been unable to confirm Captain James Kirk is the true originator of the classic 'Kirk's Heresy' statement. Some evidence suggests other individuals favoring a more rigid interpretation of the Prime Directive falsely attributed the classic form of the heresy to Kirk. Other researchers go further, saying the classic wording of the heresy was attributed to Kirk "with forethought and malice".
An alternate wording of the heresy - preferred by some who actually advocate more frequent interference with planetary cultures - is that the Prime Directive is the highest law of Starfleet excepting Common Sense, which should and does take precedence.