Is it inappropriate to use an exclamation mark after a first person plural imperative sentence, such as
Yes, let's stop talking about that!
I am a foreign speaker of English conversing in text online with a friend who is a native speaker. My friend perceives the use of exclamation marks as shouting and feels offended by that. She pointed out the exact phrase quoted above as being offensive due to the exclamation mark.
I am aware that the exclamation mark is used far less in English than in my own native language (in German we use it in many places where English speakers would use a "."), however I remember being taught very long ago in highschool that any phrase starting with "let's" should end with an exclamation mark, to denote that the phrase is a suggestion. It feels wrong to me not to use one in this example.
Your input is appreciated.