What's proper.... where?

I was under the impression in mainland China it was correct to address
a waitress as "xiao jie".

Now I understand that is offensive.

Should refer to them as fu wu yuan (fuyen) or xiao mei.

Taiwan- Xiao Jie is OK
Singapore- Xiao Jie is OK

Obviously you aren't refering to a waitress the same is in a KTV
but what is preferred address by mainland Chinese?