The Farpool: Destiny

Amphib Charley Meyer has a mission: save her adopted world of Seome from destruction by the hated alien Coethi. But the mission is both dangerous and illegal, violating Time Guard’s General Order Number One.
She tries to sabotage the Uman weapon known as the Time Twister, but she fails at this. Now desperate to confront and divert the vast interstellar swarm and stop future conflicts that will threaten Earth itself, Charley flies her ship right into the heart of the Coethi swarm to try to negotiate with the Central Entity.
But what she discovers about herself changes everything.
Now trapped inside the swarm and displaced to times from her own past, Charley makes an incredible discovery about the origins of the aliens.
Armed with this knowledge, Charley realizes her mission has now changed completely. Realizing the Coethi and their Imperative cannot be stopped, she blends her new understanding with a bold new idea, an idea that preserves the time stream, possibly averts interstellar catastrophe and sends Charley on a mission that she can scarcely conceive of.
Final title in The Farpool Stories.