I don't know for sure, but I suspect Tina has had an opportunity to "chase the ring" so to speak, but more as a complimentary piece, than a featured part of the offense. There was speculation a few years back about joining the Aces when they were top contenders, but that didn't go anywhere.
It could have been many things, but money might have been an issue too. The Aces were able to compliment their stars with good vets who were willing to play for less than market value while ring chasing near the end of their careers. Get maybe one good big backup, one midsize, and one guard, spend as much of your cap as you can on the top 8, near minimum on everyone else, and at least some of the backups at an obvious bargain because they wanted the ring. Tina might not have been willing to take less, I don't know.
Tina might still get that ring, but money, and her legacy with career stats, are also factors and to a certain extent there could be trade offs there.