Ni soy divorciada ni estoy casada

Ni soy divorciada ni estoy casada
 

Hi,

Is there some internal logic in this ser/estar case, or do I have just to memorize it?

Both 'ser divorciado/a' and 'estar casado/a' are correct usages describing one's marital status, but so are 'estar divorciado/a' and 'ser casado/a'.

Which verb to use greatly depends on the speaker's perception.
When giving marital status, the verb ser generally suggests a longer length of time has transpired, while estar usually suggests that a change has occurred since the last time the two conversed.