So if your viewpoint character can’t see herself, how do you describe your character to the reader?
Through other character’s eyes in other sections of the story.
You really don’t need to give a full description of every character, all in the first chapter. I’m totally serious, here.
If you start out chapter one in Amelia’s point of view, you don’t need to make sure the reader knows Amelia is petite, dark-haired, and sexy.
You can save that for chapter two when Gaston finds himself attracted to his new neighbor, who is petite, dark-haired and sexy.
Also, remember that your character won’t notice things that are commonplace, so she won’t toss back her long, ebony tresses as she walks to her car. She probably wouldn’t even notice what she’s doing.
Instead, have the next scene start from Gaston’s point of view as his attention is initially caught by the sunlight glinting off of hair so glossy, it’s as if it’s made of strands of onyx.
Using a mirror to describe your character is extremely cliché. It’s also sometimes seen as lazy writing because the writer can’t come up with a more creative, unique way to let the reader know what the character looks like.
Some writers use a mirror to show how the character views herself, but there are other, more creative ways to do that—with dialogue, action, or snippets of thought in response to specific things that happen to her. Be original!