Need a short escape in europe!

If your budget is small, I would suggest you drop Switzerland. Amsterdam would certainly offer good options for your age range, as well as lots of indoor options if the weather is bad, but it will be more expensive than Lisbon. So you'll probably have to balance off budget versus the activities that most interest you.

Lisbon might be the cheapest to eat and sleep, but unless you research bus routes, has fewer connections than other capitol cities, and might be more expensive to reach. It wasn't too cold last month, either, when we were there. Amsterdam is a classic student destination, and I think you would enjoy it the most. I'm sure there are hostels, but Switzerland is in general too expensive for you. There are lots of spas all over Germany, but everywhere, I'm sure. If you don't mind chilly hiking, how about Freiburg (im Breisgau)? (Check on student train deals for day trips-Freiburg doesn't have the KONUS card.) Antwerp and Gent are classic student destinations that are smaller and less crowded than Amsterdam.

I'm not positive it has enough for four days, but Lille is idea for train reasons. I believe it is possible to visit Bruges from Lille, which you would like for one day.

I suppose the ticket home is already bought? You have to leave from Paris?

Why don't you just spend your extra 3 or 4 days in Paris? You have to depart from there to Canada anyway, and the city is wonderful at Christmas time.

Amsterdam for a party, the Alps for skiing or snowboarding (and a bit of partying as well).

3-4 days is not much. To get somewhere where you have to fly would take too much from it. That would eliminate Lisbon. You can get to Amsterdam in few hours by fast train. But the weather will be damp, cold and likely rain. Swiss Alps are expensive. But why not instead French Alps? Austrian? But those are quite farther away. I would suggest cheaper destination like High Tatras in Slovakia, Transylvanian Alps in Romania or Rila and Pirin mountains in Bulgaria. All beautiful and relatively cheap but 3-4 days is to little for that considering the time to get there and back to Paris. So in your situation I myself would go for French Alps. But if you want something warmer then French Riviera. Still not beach warm.

Flying to Lisbon would really eat in to your limited time.
Let's assume you do get a late flight on the 16th, depending on your departure time for Canada on the 20th, you may have to fly back to Paris on the 19th. Possible flights with easyjet work ...

Wednesday, 16 December 2015
easyJet EZY3763
21:10 CDG Paris Charles de Gaulle
22:45 LIS Lisbon

Saturday, 19 December 2015
easyJet EZY3762
17:35 LIS Lisbon
21:15 CDG Paris Charles de Gaulle

Thank you for valuable advice. If I choose the French Alps, where exactly? If I choose Paris, what would you recommend? I have been to all of the major art museums, the catacombs, Versailles Palace. What would you recommend next? Where should I stay and get some relaxation?

One town in the French Alps that you could consider is Chamonix, although it's a bit on the posh side so may not be as good for those on a tight budget. The easiest way to get there from Reims would be TGV to Geneva (about 5.5 hours) and then Shuttle to Chamonix (about an hour). Travel all the way by train is possible, but it travels a slightly different route so takes considerably longer. There are good TGV connections between Geneva and Paris, which will be convenient.

Pre Xmas atmosphere in Strasbourg and/or Lyon ??

I would also say Chamonix. The view of mountains is awesome.

The first year I lived in Paris when I was about your age, I just wanted to see the ocean and de-stress after so much Parisian metro/bulot/dodo, so I got on a train during Christmas break and went all alone to St. Malo for a couple of days. It was gray, wet, no tourists, but it was Brittany through and through. I stayed in a dump above a cafe and ate like royalty. I loved it. Otherwise, I'd go have a good time in Amsterdam or Strasbourg, too.

Ken has pointed out the problem for going to Chamonix - it will take the better part of a day to get there. And you will need another day to get back. Then there's the problem of not being near your departure airport the night before you fly.

When do you have to be at the Paris airport for your flight home? If you fly somewhere, are you ready to rely on getting back in time if there's a weather delay?

From Champagne-Ardenne you can get the TGV to Strasbourg. Visit the Christmas markets in Alsace. Or in Paris.

If you have a tight budget I think you would be wise to eliminate Switzerland and spa visits.

I would just stay in Paris.. trust me.. you have not seen even a portion of it.. I have been going for years.. for weeks and even months at a time.. and I have still got lots more to see...there are over 200 museums.. and even more historical sites.. but best of all.. I find it very relaxing when I am solo..
I pick one thing a day to visit . and the rest of the time I browse book stores, shops of curios, sit in cafes reading and writing.. sipping a café crème.. walk along the river.. find a pocket park and sit on the bench..

Its only as hectic as you make it.

My second choice would be Amsterdam..

I think going to Switzerland for only 3 days sounds hectic and the opposite of relaxing.
Spas sound awesome.. but my limited experience in Zeramatt showed me they are definitely not for budget travellers.