Go for it!
First of all, have you thought about a possibility for her feeling the same way and wondering whether you're interested in something more or not -- you both were trying to keep it very professional, therefore it might be hard to understand now "who was thinking what". For both of you.
It might be that she wanted to drop a little teaser so that you would come back to her and technicly, you would meka the 1st move (a way for a girl to go the "safe" way, without making a fool of herself). It might also be that she just liked working with you and wanted to keep in touch with the nice colleague she has.
As you really have just a few days, and then you might never ever see her again, I would say, why not to try? Even if she's not interested in you, you will never know until you try. Ask her out for dinner (saying that, well, after all these years, you would like to have say a worthy goodbye or something), then when you're out, speak about the best projects you had with her and how good it was to work on them with her, and see how she reacts. If she seems ok, then you can do whatever of the following -- ask her to the dancefloor, swith the topic to anything else than just work, finally, tell her directly something like "I kinda got to like you during these years, you know?" Just like that, very innocently. Just don't mention the 100 miles from each other fact as long as you can.
Well and after all, try to softly go the right direction to get her opinion about your further relationship. I think it always works talking just hints. If everything seems fine, your final aim is to fet her agree on the next meeting. Agree on the exact meeting time and place -- "we'll meet someday somewhere" never works. "We'll meet in Paris on the 5th of August, I will take 5 days off so I will leave home on the 10th of August" -- that's the way it should sound. To achieve it, it's best to use the "choose on of 2 options" tactics. She says -- so we'll meet again. You say -- July of August. She says -- August sounds better. You say -- 5th or 23rd? And so on, until you have a clear plan
So that's what I might offer. I must just note that I've been in quite a similar situation myself, and I still regret the guy did not agree on the 5th of August... You are in a win-win situation -- there's nothing to lose. Go for it, and let us know how it worked!