So the word basically means that Sakura is immersed in poison when it comes to Sasuke.
Japanese is a really subtle language, the wordplay is there and we all know how much Japanese people use symbolisms. And you can see how this is a very negative word.
Then he went on saying that there are other terms to describe the addiction
that wouldn’t sound as negative or derogatory (like this one, that would explain PERFECTLY a “healthy” addiction caused by infatuation). But that’s the word he chose.