2 long stays in EU, base SEA, help needed
 

I'm gonna ask for some real advice here, because there is so much knowledge, and I can't seem to figure out descent strategies on this one...
My girlfriend is going to stay in france(NCE) for the summer ~may15-~aug15 and norway(BGO) from ~sep15-~dec20.
Given the long stays, the low fares are generally unavailable and summer period doesn't help much.
She doesn't mind 18 connections for that sake or some train riding, I have educated her in MRing already :D
She has ~6000 YTD EQM on OnePass and ~3000 on MileagePlus. No status in either. No specific travel patterns, only the occasional getaway.
Any advice would be greatly appreciated!

I know you're seeking cheap airfares and I can't help on that. But here's a potential problem you might warn your girlfriend about.

France and the other EU countries, plus a few non-EU countries including Norway, are parties to the Schenegen Agreement. This agreement states that a US citizen can only stay in all of the Schenegen countries combined for 90 days out of any 180 day period. Going to a non-Schenegen country does not start a new 90 day period. Now some will note that there are not a lot of people running around enforcing this rule, and for all I know, that may be correct but she should be made aware of this rule anyway.

She is getting a visa for both countries. One for working and one for studying.

you could try to nest the tickets, as the inner one is only a month appart.

Also for the european part there may be more than enough lcc.

perhaps there is one airline where two one ways work that far appart

I tried ita but it does get timed out with that request :(

It may actually be cheaper to buy miles and get your girlfriend those two one way flights at the end of it and use a nested flight in the middle.

Get on the phone with your favorite airline and let them do some searching - i find that most call center lines are actually helpful and the more complicated your problem is the more worth is the invested time in them. ;)