Those are two separate things so we can handle them separately:

NaCl in the galaxy as a molecule.

Nope, by mass and density it's actually going to be pretty far down.

There's a table of the elements by how frequently they get created by stars and you'll find that while their not uncommon they are pretty far down and pretty far apart.

So finding both together is even lower than that.

Now the second question:

Water being salt water.

That one is a bit more tricky to detail but in short:

Salt is really really easy to dissolve. In water.

What that means is that any body with liquid water in it that also contains masses of salt will dissolve on in the other unless luck keeps them separate.

And once it's in it's very very unlikely that chance will separate them again.