Dan raises an excellent point: is the standard for determining whether Elaine was subject to imminent threat of death or serious injury, so as to justify her weapon possession, an objective standard ("events as seen by a reasonable person"), a subjective standard ("events as Elaine saw them"), or a mixed standard ("events as a reasonable person in Elaine's position would see them")? If Elaine's actual belief is irrelevant, then arguably her state of mind is irrelevant, and thus even her own contemporaneous statements indicating state of mind should be inadmissible hearsay if she offers them through other witnesses.
Twenty minutes of research - all I have for now - doesn't give a definitive answer. I would go with "objective", though. The case law supports the actual language Lange requests: "During the time period alleged in the count Elaine Brown was under an unlawful and present threat of death or serious bodily injury." Not "believed she was", but "was". See, e.g., United States v. Deleveaux, 205 F.3d 1292 (11th Cir. 2000); United States v. White, 552 F.3d 240 (2d Cir. 2009). That sounds like an objective standard. If so, that's going to be exceedingly difficult to meet.
As for the discussion with JRB over state-of-mind hearsay, I don't think we're saying very different things. Iff Elaine's state of mind is relevant at all, the only witnesses who could testify to what otherwise would be hearsay were those present at the time of the charged events. Those folks clearly have a privilege to refuse to answer, and would have to be fools not to claim it.
Hmm. What else would they have to be?
"A wise man proportions belief to the evidence."
- David Hume