If she just got out of a serious relationshp, she'll need time to grieve. I supect if you remain available and she's truly interested in you, she'll come around.
As for dealing with the pain...there's the tricky part. The only way I've found to handle that is to make certain I fully accept that the other person may never actually want me and that particular relationship won't ever happen. Once I've accepted that as an outcome, the pain subsides.
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.