Oof! That's a rough one. My last paramour was long-distance, though only a four-hour drive away, so I could visit with reasonable frequency. That's not quite the same situation as living in a different country.
As for having the discussion about her dating someone else, well, I don't see any compelling reason to delay having that. You can discuss it on the phone just as well as in person.
Of course, if she begins to date him in between now and your visit, she'll likely be in the throes of NRE when you get there and your visit could feel just odd because of it. So it could be a good idea to ask her to wait.
I prefer to have all potential partners meet Curly before any serious dating begins. Were we living far apart, I don't think I'd insist on that sort of thing as it'd be really impractical. Hmm. That sort of distance seems to involve quite a bit that I'm not conversant with, so I'm not certain I can help much.
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.