Hi !!!
Tierney is too strange in my opinion.
It seems a surname and I can't see it on a girl anyway.
Its sound is not appealing at all.
After that its meaning is "lord" and it was originally masculine, so I prefer a different form of it that is
Tiarnach for a boy.
A name with a similar sound that I prefer for a girl is
Tansy. It would be better as a sibling for
Florence.