Work-release. It might even be part of the plea-bargain plan, although Team Flash probably expected the eventual threat to be Godspeed or Thawne rather than the personification of the Speed Force.
Cisco held a gun trained on Barry earlier this season, which Cisco should have known was pointless. Speed Force Nora is presumably faster than Barry, but as long as the show is being inconsistent about people's reaction times, I think we just have to accept that guns can defeat speedsters. And there's always Velocity-X, to give Speed Frost another scene.
I think the big problem with this idea is that the title character needs to be the decisive factor in the victory. Maybe Barry can be busy dealing with an even bigger problem while Frost fights Nora.