Urgh, so we had a bit of a falling out today. In essence, I said that it feels like we're drifting apart (which in hindsight may not have been smart) and she flew off the handle. She's effectively said that I need to commit to her fully and "show" it (no idea how!), or we're done.
If you feel that way, there's no point in keeping quiet and pretending different. If that's what you feel, then that's what you feel. It's not a good sign for you to tell her what you're thinking, and she gives you an ultimatum and some kind of vague and impossible task, with the threat of her dumping you. How about she does something to help you deal with the fact you're feeling neglected and abandoned, instead of offering to dump you if you don't pretend everything is fine with some grand gesture to make her feel good?
Frankly I've no idea how I'm meant to commit to her fully when she's only home quarterly and there's little evidence of her working particularly hard to return home on a permanent basis, but equally it seems silly to let it drop now before we see each other in late June and decide what to do when we're face to face.
No idea what to do. She's lovely and were she here I could genuinely see us being together for a long time - possibly forever - but I'm quite rational whereas at times, in discussions like this, she hears what she wants to (or doesn't want to) hear and utterly loses it.
Well put some of the responsibility back onto her. What's her commitment going to be? Tell her if she sorts out her stupid job and makes a commitment to actually be with you, then she'll get a commitment back. It looks like your June meeting is going to be a crunch time and you're going to have to decide if you are going to be together or go your separate ways.
The problem in your relationship is being apart because of her job. If she can't or won't work towards fixing that in some meaningful way, then put a fork in it, the relationship is done, either now, or twelve months from now when you've got fed up of waiting for her.