Indeed; before this weekend, she was a commoner.
Now she's a Duchess. The Queen also, by convention, allows her the style "Her Royal Highness". Though she is a princess by marriage, she's not a "princess of the blood royal", i.e. descended from a monarch, so she's not styled "Princess Meghan".
It's amazing how complicated and subtle this all gets. It's almost as though centuries of tradition have carried forward through multiple nations and dynasties. (-8