There is no terminal (or concourse) E at IAD - from United flight status that appears to be her arrival terminal at PDX.

IAD-PDX almost certainly will leave from Concourse C or D, which are connected (flight status doesn't show a gate yet). When she arrives at IAD she should be able to use the "transfer" passenger route, which keeps her in Concourse C to clear customs, she'll then re-check any bag go through security, and be in Concourse C "airside" so she can go to the lounge.