why does she say nida ? what does that mean ? 0_0

Its an exageration.
In the korean language, when you talk, a lot of sentances end in nida,
for example kamsahamnida
However no one says nida after EVERY sentance.

its sort of like "no" in the japanese language, it doesn't have a certain meaning, but the sentance would be broken japanese if you didn't say it, in some sentances.