6 cops? Hm...what exactly did the parents report?
In any event even if you and the Gf flee to another state it won't eliminate the minor int eh legal state of residence issue. What that means is that she'll still be considered a runaway.
Running away is a status offense in NE for the runaway. This means that the police can be involved and bring the child home. Additionally anyone who provides shelter for a runaway or interferes with the retrieval of said runaway for more than a few hours and the runaway doesn't return home intact can be charged with contributing to the delinquency of a minor. Leaving the state can certainly up the ante and she'll show potentially show up as a missing person.
What all of this boils down to is that your plan is a terrible plan. You're already harboring a runaway and encouraging her to not return home. In NE that is a crime. It's possible that the fact that you're also a minor will provide some mitigation but of that I can't be sure.

