Didn't an answer from Hasbro say that there was a full Thirteen in the Bayverse, which the Seven Primes were half of and the other six just didn't have Prime in their name (or die in the same place)?
In hindsight, that felt more like a band-aid kind of answer since it was something that Hasbro never actually followed up on. The little teaser at the end of the answer ("Our future plans include telling to story of this epoch soon.") never actually came about for the Movieverse version of the Primes, with it now being evident that what this was alluding to was the story of the Aligned Thirteen, which Hasbro tried to make be its own thing and fully ignored what ROTF and the other movies were doing (and didn't even stick to that "only seven named 'Prime' in the Thirteen" answer at all).
And technically the Bayverse is also part of the multiverse that had the multiversal singularity version of the Thirteen
Which was yet another thing Hasbro was trying to get away from when promoting their Aligned stuff, as seen in other answers given only a year after the aforementioned one about the Thirteen.
and Quintus Prime wasn't on the full list for that version that we got from AVP.
The AVP answer about the multiversal Thirteen was also written by individuals who had nothing to do with the Hasbro Q&A sessions that original made that "only seven named 'Prime' in the Thirteen" claim.
except for the one continuity where they actually did do that.
In which Quintus wasn't a thing yet, either.
I get the feeling they didn't want too many evil dudes in the 13 after Liege Maximo and (ugh) Megatronus.
The biggest irony of this being that the Covenant book that finally laid out all of the Thirteen chose to actually rewrite Megatronus to make him
not evil, but instead the misunderstood victim of Liege Maximo's machinations. Rather than Judas, he's now Othello.
...And then RID 2015 would go and pull a 180 on that by just making him evil again. Okay, whatever.
the title "Prime of Life" is so specific to Quintus Prime's whole deal I can't help but think she's either the Bayverse version of Quintus or one of Quintus' creations masquerading as him.
Or, here's a thought. What if she's actually not related to the Cybertronians at all, but a completely separate alien creature simply pretending to be a Prime for her own selfish ambition?
Like, maybe Unicron had once destroyed her home planet in the far ancient past, and now, to get her revenge on him, she impersonates a Prime in order to get the Cybertronians to kill Unicron for her, not caring who she has to manipulate along the way?
(Do we see her actually creating life at any point in TLK?)
Nope. Not at all.