I imagine Jane is tone deaf (not listening to what you're sayiing with any empathy) because most folks tend to be tone deaf and superimpose their own situations and reactions on what other people say. She would only consider sex with somebody else to "spice things up," so she projects that on you.
It's not that she has something against polyamory, per se, it's that she's only considering your situation as if she were in it. I suspect further discussion where you make clear that the polyamory has nothing to do with the lack of sex would help her into your headspace and out of her own.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.