Yes, she can be appointed as judge, but it is makrooh tahrimi, i.e. doing so is near haram. It is mentioned in hadith:
Ù„Ù† ÙŠÙÙ„Ø Ù‚ÙˆÙ… ÙˆÙ„ÙˆØ§ Ø§Ù…Ø±Ø£Ø© Ø¨Ø®Ø§Ø±ÙŠ Ø´Ø±ÙŠÙ
It means that a nation that makes a woman their ruler will never succeed, hence woman should not be appointed as judge.