The constant back and forth insult wars that Eve and Summerset have been carrying on over the last 50+ books is a staple of the whole series. They used to do it because there was very clearly an animosity between them. But after a while, they started to actually care about each other. So, while they may still snark at each other, there are many moments in this series where we see how much they do care about each other.
We talk about some of the favorite Eve and Summerset insults, as well as some of the times when their caring for each other really comes through.