When I learned the word 太太, I was also told that you would not say "这是我的太太", because using 的 with people would sound too possessive.
Now, the other day I was saying goodbye to a native Chinese chat partner, I wrote "再见，我朋友". And he didn't understand. When I wrote it in English again, he said that it should be "再见，我的朋友". I asked him why and what I had learned, but I wasn't able to really understand his answer.
So, can someone please explain to me when to use 的 with people and when not to?
Your question should be " when can I omit the possessive 的 "
The adjective suffix 的 cannot be omitted when it is needed. For example: 强大,勇敢的人；身形高大的人; Adjectives that do not need adjective suffix can directly apply to the object. For example 好(good) in 好女儿(good daughter)
The possessive 的 in 这是我的太太; 他是我的女儿；陈先生是我的上司 can be omitted to 这是我太太; 他是我女儿；陈先生是我上司 when there's a verb to act on the object, for example 是 is the verb and 我(的)女儿 is the object.
You cannot omit the possessive 的 when there's no verb to act on the object . That's why you have to say 再见了, 我的朋友 but not 再见了, 我朋友.
Unless you also omit the subject. In this case, 我. Then you can omit the possessive 的 along with the subject and write 再见了, 朋友.
More examples:
In 你打了我的女儿 - 打 is the verb and 我(的)女儿 is the object, therefore, you can omit 的 and write 你打了我女儿
In 你好吗？我的好女儿，there's no verb to act on the object 我的好女儿, therefore, you cannot omit the sentence to 你好吗？我好女儿
In 我(的)上司是陈先生 - 我(的)上司 is the subject, 的 can be omitted'
In 我(的)女儿打了人 - 我(的)女儿 is the subject, 的 can be omitted
