If Shea's ultimate career goal is to be the UConn head coach, then the best move she can make is to get a head coaching job somewhere in the Top 100 of WCBB, and develop an independent record of success in that role. That is exactly what Carla Berube appears to be doing. It is what Jen Rizzotti has attempted to do, but without (at least recently) the requisite level of success.
It is too risky to promote an assistant who has never been a head coach anywhere -- too much chance of a "Holly syndrome".
However, I would make an exception in the case of Sue Bird. Her name recognition with potential recruits (which Shea / Carla / Jen do not have), her obvious leadership abilities, and above all, her knowledge of the very highest levels of basketball worldwide, reduce the risk to an acceptable and even miniscule level.