he feels weird about her not wanting to show any emotion. (happy :) sad :( angry >:( ...)

What are signs of emotion? A smile is a sign of happiness A frown is a sign of displeasure A yawn is a sign of boredom. Any of these signs would show what she was feeling. But she refused to express these signs making it difficult for the author to know what she was feeling. This difficulty made the situation awkward.

It means to show how you're feeling; trying to not smile, or trying not to cry, for example.

same ask