Mitochondria-DNA-Test: Aunt (Mother’s side) with Niece or Nephew

F. grew up with foster parents. She does not know her biological parents. About a month ago a lady got in touch with her and claimed to be her mother’s sister (F.’s biological aunt). F. wants to have this confirmed. A Mitochondria-DNA-test makes this possible, if this lady really is her aunt they would both have the same Mitochondria-DNA