You should see my girls wiggle dance. If they had hips, those hips would be a-swivelin' like crazy.
Is the spot on her belly white? That would be her ovipositor, or eggspot. All girls show them but when they are ready to breed, it can stick out a little more than usual. If she's really ready to breed, she might egg up. If that's the case, she might look a little bloated for a day or two. I'm not sure how active she'd be if she's never seen a male but it's possible she's hyper because she's looking for a mate.
The best way to take the salt out is to do a complete water change. Or, you could do half one day and half the next day. That should get the salt out.