How to describe a sinister expression

Question

I'm a noob at writing and I wanted to find out how to describe someone's face contorting into a sinister expression. I'm having a bit of trouble doing so. The most prominent features I want to focus on are the eyes, brows, and smile. Here's a sample of the text:

"The somber sounds of a heartbreak fade and in it’s place were mischievous muffled giggles. The façade shuts off. Then Jenny rolls onto her back, uncovering her face from her pillow and revealing an uncanny expression. Her eyes were red and wet and a little dribble of snot dripped from her nose. But her facial features unveiled how she really felt: [description of sinister expression]"

Answer 1

In writing, most facial expressions are open to broad interpretation and lead to less immersive description — by that I mean they rely on more intellectual or rationalizing interpretations than evoking specific emotions.

While it's good to use character facial expressions to make the storytelling more immersive — reminding us there are people filling the space that the pages inhabit — a sharing character’s reaction is a much more powerful technique since it can evoke the reader's memory of when they either encountered a person like that or expressed that emotion themselves.

So rather than say 'she had a tight-lipped smile' or 'she only smiled with her eyes' use 'her smile made my blood run cold' — Okay, it's a trope, but I’m not going to give away my best stuff for free — or 'her smile reminded me that winters didn’t last, that summers followed, that I shouldn’t give up hope.'

Sharing character reactions to events is a very powerful technique to communicate subtle and moving emotional elements and moments in a story.