She could run... but forming a NEW party. Running as a Libertarian would not be a good idea.
The only reason I am suggesting forming a coalition with the Libertarian Party is because they are the only path to ballot access at this late date.
The two-party system in the US has thrived because of the many comments above. If we borrowed (for this election) some of the coalition-building style of the parliamentary system, we could get the fiscal issues front and center. And the majority of the country supports that.