1) Does her friend write a
letter to her aunt?
Does her friend write a letter to her aunt or to her friend?
Who writes a letter to her aunt?
Her friend writes a letter to her aunt, doesn't she/he?
Whom does her friend write a letter?
2) Can your mum cook pies?
Can your mum cook pies or pancakes?
Who can cook pies?
Your mum can cook pies, can't she?
What can your mum cook?