Should a GLO expand at all if chapters are folding due to numbers, or should it protect what it has already?
No. Take care of your own first. Don't have a 4th child if you can't support the 3 you already have. Colonies take up a lot of time and resources...resources that could go to help the chapters that have been around for 10/20/50 years. Yes, maybe a colony doesn't have the "battle scars" of an old chapter, but sisterhood is supposed to be about doing the right thing and the caring thing, not the easy thing.
Should it put more emphasis on recolonizing closed chapters?
Yes. There are a lot of alumnae wounds out there due to closed chapters, as we have seen on here. When the time is right, if it's between reopening a closed chapter and opening a new chapter, this shouldn't even be a question. Too much history of our GLO's has been lost due to hasty and faulty decisions.
Is it important to expand internationally (to Canada) if you are US-only now?
Perhaps the Canadian universities would be more friendly to the idea of Greek life (as I understand they largely are not) if more groups chose to come there. But then again, a lot of groups don't want to come to an unfriendly environment. Chicken, meet egg.
Best strategy in general? DIVERSITY. If your GLO says "we only expand at small/big/private/public schools" that is not a niche. It is a box which you will find yourself trapped in. Fraternities perhaps can get away with this more than sororities since there are, simply, more of them...but if a sorority starts passing up great opportunities because "we've never done that before" or "that's not our niche" you best get the hell out of the NPC.