Related to the stuff I highlighted in red above, and I recognize these are discussions of other people not necessarily #12 in 21; I don't know that the Seattle Storm has the option to release two players to pick up Gabby Williams. Whether Gabby is a free agent or still contractually tied the Storm, I don't think the Storm can release two. The league has a requirement of a minimum of 11 players on each team, and Seattle is currently at that minimum roster. Releasing two and adding one would reduce their roster size down to only 10 players.
And, there is the Team Salary Cap that must be attained to. With that regard, I believe the Seattle franchise was pretty darn close to spending every dime possible on the eleven players they have on the current roster. In essence, it would have to be a one for one; someone on the current roster out, with Gabby not being paid any more than that current player's salary.
If Gabby demanded the equivalent of a $200,000 salary (I say equivalent because half the season is already over), then the team would have to cut Jewell, Nneka, or Skylar to open up that $200K. Would the Storm even consider that? What does the word "Protected" mean contractually in the WNBA - is it possible to just cut a protected player and not pay them their salary? If not possible, would Gabby accept considerably less; they only pay Vivians $76K, would that be enough to entice Williams? What are the possible 'trade' or 'release' options for Gabby to get out of Seattle? How does she just become a free agent? And of course, virtually every other team is going to be in the same boat as the Storm, right? There is at least one that she would not consider even if it were a league maximum contract, given that they previously "did her dirty!"