My major complaint with the Bì Xié is that it has too few HD to justify all its attacks, special attacks, and special qualities. It should have more like 11 HD.
The stat block is a bit of mess but I don't have time to go thru it today. You obviously changed it from Large to Medium but haven't updated the stat block so a lot of numbers are off.
I think I have a Rhinemaiden already.... Let me see if I can find it.