Gravity Waves. Alien Affairs, #4

Half-alien, Terrie Deshler, and her alien bashing mother, Carrie Player, surf the multiverse when they hear that Deshler, who tried to annihilate the human race, is in trouble for failing in his mission. The only way that they can reach Tau Ceti IV in time to intercede is to go back in time the thirty-two years it takes to make the transit, which also resets their ages. Then there is the minor issue of a marauding race of aliens who are looking for a new planet because theirs will be incinerated by a supernova.
One more time, the Alien Affairs teams must save the human race, but this time they have the mind-twisting force of the multiverse to wield as a weapon more powerful than gravity waves.