mtDNA and adoption

[MaryAVM]

Just wondering if there has been any recent news about the absolute validity of mtDNA testing.  I had my mtDNA done in 2006, and the results showed a haplotype of "A".  My sister(deceased) had a female child she gave up for adoption in 1958.  I was too young to remember the exact details, but with the knowledge I did have, I located an adoptee on a website.  We exchanged health information and photos, and the similarities were uncanny.  Since I had done my DNA testing with FTDNA, I referred her to do the same.  We did not match.  She resulted in haplotype "U2", and we had only two mutation matches on the 12 value test.  Neither of us have a lot of money to keep redoing tests.  I sent my sample to SMGF to double check it, but it was sent months ago, and not resulted yet.  My daughter sent to SMGF as well, but no results yet either. The "potential niece" has not sent to SMGF because she does not have any generations to send with her sample--she knows absolutely nothing about her birth parents.  

I do have two nieces, daughters of my deceased sister, but they know nothing about the birth of another child.

Thoughts anyone?

MiMi

[marilyn]

Hi, MiMi.  The mtdna testing result is almost never wrong (occasionally there will be a minor error, which doesn't change the haplogroup.)  So, it is a safe bet that you and the young lady do not share a common maternal ancestor.

One possibility you might consider is to test one of your nieces, to confirm that they match you, which would confirm that you and your sister share the same mother.  (which I assume is a very high probability.)

The most obvious conclusion is that the young lady is not your niece. 

I hope your continued search will be successful.

Best regards,
Marilyn

[anngmones]

Hi, Mimi
I agree with Marilyn. Enjoy a new friend but it is a needle in a hatstack trying to find a child that was adopted unless you have more information to go on about the adoptee.
anngmones