I read this in UK, I think it was hardcover, possibly early eighties.
A woman is mind transferring around the galaxy for the 'good side', she is trying to get various organisations to unite against the common enemy who want to destroy everything (I can't recall any names or description of the bad side)
As part of this she shunts into the body of a female slave on a starship. The starship owner is an alien who is (I think!) something like a 12 foot tall Mantis. These slavers have lots of slaves on their ships who are under some kind of mental thrall to obey. However the Mantis are also technically on the good side and sometimes coordinate their fleets to fight in alliance, this is what the female protagonist has been sent to achieve.
When she gets aboard she swiftly learns the enemy had got there first, the Mantis is being held in a compulsion field so he has to obey or suffer agonising nerve pain , the compulsion field also zaps him if he contemplates escaping so he has to stand there basically thinking happy thoughts. To keep him alive his slaves take him food and rub oil into his chitin etc.
Somehow, without consciously thinking of escape, he manages to communicate to his slave girl that she should throw his food over him when next she serves him. She gets the cook slaves to help prepare an extra large portion, even though they live a life of drudgery they prefer it to death so they assist their insectile master.
She throws the food and the compulsion field fizzles out for a few seconds but that's enough for the Mantis to sieze control and kill the boarders. She then mind transfers out to somewhere new but the rest has faded in my memory