Mi hermana es muy limpia.
However, one of my coworkers was wondering what the Spanish word for dirty was. Apparently, his sister isn't quite as nice as my sister.
Turns out you can do this to find out:
Windows+R to bring up the Run... dialog box in Windows XP
Type 'winword', press Enter to run Microsoft Office Word 2003
Select Tools | Research to bring up the Research sidebar
Here, you can select Translation. This gives you the option of a few languages, e.g. Dutch:
Mijn zuster is zeer schoon.
Even after all these years, it's hard not to read schoon as schön; remember, it's mooi, not schoon, when something's pretty.
So... you Korean speakers out there: Is this even close?
나의 자매는 아주 청결하다.