Is "další" the masculine form of another? Is there ever a time when it would become dalšá? Why does Katerina get a masculine form (if that is what další actually is)?
IMO, your suggested sentence would be more likely to use jiná: "Not THAT Kateřina, but a DIFFERENT Kateřina." But další might also be used, depending on the specific context. [Edited to correct my own mis-typing when initially replying... :-/ ]
You might have forgotten to add the acute accent to the i? (i.e. další is correct, while dalši is not).
It can be hard to see the difference on some screens.