Kalifa's appearance was supposed to be bad news, but by a stroke of luck, it resolved the danger Su Xiao faced in the Galley-La Company.
As long as Rob Lucci and others don't want Kalifa dead, they won't actively provoke him. Silencing is possible, but that would require sacrificing Kalifa.
If Rob Lucci brings people to silence him, they risk total exposure. Between one person's exposure and everyone's, Su Xiao believes they will choose the latter.
Moreover, Su Xiao's previous attitude indicated that he found Kalifa suspicious because of her use of special poison, rather than acting omniscient and saying a bunch of foolish things like "I know your plans and allies."
In the current situation, the likelihood of Rob Lucci and others coming after him is even lower.
Kalifa now has a special use, not as a R|B|Q, but as a bargaining chip.
Walking along the path in the City of Seven Seas, Su Xiao felt good, although he was unsure where to go.
