Here are the feminine forms for the terms you provided:
- Nephew → Niece
- Wizard → Witch
- Prince → Princess
- Stepfather → Stepmother
- Bachelor → Bachelorette
- Bridegroom → Bride
- Heir → Heiress
- Lady → (remains the same, "Lady" is already feminine)
- Emperor → Empress
- Queen → (remains the same, "Queen" is already feminine)
- Duke → Duchess
- Hero → Heroine
If you need any more assistance, feel free to ask!