We often use (nvshi),but it is very formal。you can use(meinv) if you want to say hi to a girl .don't use (xiaojie or guniang), it is so ambiguous that will raise our unhappiness

xiǎo jiě (小姐) is used more often than gū niáng (姑娘) in Taiwan. For example, you can say, "xiǎo jiě , nǎi de dōng xī diào le (小姐, 妳的東西掉了)," when you would like to tell a lady that she had something dropping on the ground. Although gū niáng (姑娘) is seldom heard, the address has some subtle meanings when females heard someone call them gū niáng (姑娘). It depends on who address them as gū niáng (姑娘).

yes,they are.

Yes, they are still used nowadays. If you use gu niang to address some young ladies face to face in my city, which is Beijing, it has a funny nuance because this expression sounds a little ancient, like you're mimicking ancient Chinese people so it's a little like you're making a joke. But it's just quite common to refer to some girl as gu niang(girl) or Xiao gu niang (little girl) when the girls you mentioned are somewhere else, again, in my city. Xiao jie is a controversial expression in China. Usage and feelings attached to it varied by region. In some parts of China, it's quite common to address some lady as Xiaojie, but in others, people use it to refer to someone who provide special service too much that it has changed the general meaning of this word, which makes many young ladies hate being addressed by this word, and they may walk immediately away from the person who call them that.

I think xiao jie is more popular.