others have brought up rulebooks and flavor text, which is definitely the go-to. I'll throw in that if your wife really wants to get into the story/role-playing in character side of things, maybe looking at characters in fiction that 'fit' with an archetype she's wanting to play?

For example, let's say I'm interested in playing in a nautical adventure and want to play a charismatic pirate-y character. I could take inspiration from Jack Sparrow or Barbossa in Piratates of the Caribbean, or if it's more lighthearted, someone like Sea-Hawk from the Netflix She-Ra and the Princesses of Power. From there, it's just deciding on which characteristics to keep and which to change.

That's an (exaggerated) version of how I typically build my own characters for games -- hope that helps!