You are so thoughtful, I applause on the behalf of your gf for
your kind & caring thoughts. 
There is many things you could do without disturbing her workload
and yet you could bring your concern love message across. You could
write a small letter, folded in it and place it somewhere she will
bound to see like wallet, bag, etc, *not* telling her all that
mushy stuff etc (I mean you could put also lar), but rather message
that convey ideas of encouragement. This is very important, at
least she will know that you are bothered over her stress and
well-being.
You could also buy small gift or her fav food, put it her at work
place, house, letterbox, etc, so when she sees it, all this small
little surprise will touched her in small ways. And of course when
you do get to see her, treasure the time spend together.
Cheers
