太太，奶奶，大姐，阿姨，女士，and many other variations are commonly used to address older women. 小姐 is used to address young women. Would it be a complement or an insult to address a middle aged or elderly woman as "小姐"? I'm in Taiwan here, so we don't have to worry about people thinking we're calling them prostitutes.
In china（中国）， don't ever use 小姐 to address them (sales girl, waiters, etc.).They will totally ignore you.
Example : 'when you want to purchase something and ask for help from the shop assistance' - 对不起小姐,请问这多少钱？ -'even though we know that in English it is a polite sentence to call someone' - Sorry Miss, may i know how much does it cost?
Because for them(china ppl) 小姐 is represented as a
Bar Girl. Therefore, you have to call them as '服务员' .
In other country, yes. You can address young women or middle aged woman by calling 小姐， for older ladies 大婶 / 阿姨，oldest ladies 奶奶. That would be more cordial