Yes, there is theoretically valuable shit in space. No, it is not more cost effective than the expense of mining here, and until it is, this will remain another one of Brianna's "I wish for Firefly, but IN REAL LIFE!" ideas. Nobody is going to throw billions of dollars at a literal moonshot with that many variables and risks.
To be clear, mining here on earth is a dangerous task that kills people all the time, and we live here. We have hospitals and emergency services and have been mining here for millenia, and people still die doing it.
Now try doing that, but out in the cold vacuum of space a million miles from home with the caveat that if you don't bring back a literal mountain of precious metals, you won't even break even from getting out there.
What interests me more is her promise to support "robotics". Robotics in what sense? Is she promising to support automation and the continued death of American industrial jobs? In a blue collar steel workers district? Has she been hitting the pipe?
Were I a District 8 resident, I'd be demanding to know what exactly she's promising by offering money for "robotics", because if it isn't some "let's build real life gundams" nonsense, then it's the same process that killed much of the American middle class in districts exactly like the one she's trying to represent.