I'm sure you are not a troll -- I visited Norway a few years ago and learned trolls have long tails with a ball of fur at the end.
There is a real problem with teachers who practice outside their area of competence. If you can do it without getting lots of school problems, you might share some of the following with her.
None of the proposed "end of world" scenarios have any scientific basis.
As to the Maya, it wasn't until 20 years ago or so that we had begun to read their inscriptions, let alone understand their calendar system well. There were larger cities in Mexico and central America than there were in Europe at the time not long before Columbus arrived. And, things weren't all sweetness and harmony -- there were wars, rumors of wars, human sacrifices, slavery and all the rest 1000 years ago, or 500 years before Columbus.
Don't misunderstand the idea of "translating" a calendar. Did our calendar tell us the world was going to end at the end of the year 2000? No, it was the end of a year, a decade, a century and a millennium, but not the end of the world. December 31, 2000 was the end of all those cycles, and January 1, 2001 was the beginning of a new year, decade, century and millennium.
The same thing was the case with the Maya calendar, which was based on a cycle, in turn based on a count of 20 (I guess the Maya didn't wear closed toe shoes, because they did their math "base-20" where we do ours "base-10").
Anyway, December 21 is the end of a Tun (a Maya year-like interval made of 20 "months" of 18 days, plus some 5 or 6 extra days like our leap day, to keep the calendar in sync with the astronomy. It is also the end of a Katun (a 20 year cycle) and a Baktun (a 400 year cycle of 20 Katun). This whole Baktun cycle lasts 144000 days. So it is the end of a Tun, Katun, and Baktun (the 13th Baktun). The next day starts a new Tun, Katun and Baktun (the 14th Baktun starts) and a new 144000 day cycle starts counting again, just as they had calculated 13 times in the past.
The Maya did not predict the end of the world -- any more than Pope Gregory did when he developed our current calendar. The Maya "year" is called a "tun", and 20 of these is called a "katun". 20 katun is called a "baktun", about 4000 years, and on December 21, 2012, the 13th baktun will end, and on December 22, the 14th baktun will begin. This is just like December 31, 2000, the end of the 20th century and second millenium, and January 1, 2001, the beginning of the 21st century and third millenium. (I guess the Maya didn't wear closed-toe shoes, as they counted by 20s instead of 10s.)
Planetary alignments and galactic alignments? No special planetary alignment occurs this year. Every year at the time of the Winter Solstice, the same alignment occurs, and nothing has happened. Back in December, 2004, there was an alignment such that in the early morning, Mercury was near the Eastern horizon, Venus was a bit above that, then Mars, Jupiter and Saturn each higher than the previous across the zodiac. With all these planets on the same side of the Earth-Sun line, nothing happened.
The 11 year solar activity cycle is expected to peak sometime around mid-2013. This cycle has been going on (probably) forever, and sunspots were first observed by Galileo in the 1500s. This solar maximum is not expected to be as big as those back in the late 1950s and the one in the late 1960s.
There are no known comets or asteroids or other objects expected to impact the Earth in the future, but astronomers continue to search, observe and calculate orbits to monitor any objects which are likely to collide with Earth.
Same kind of discussion applies about any other "reason" for it.
Given all the above, I recommend the following:
1. Don't run up your credit cards and other debts expecting that you won't have to pay them back after December 2012.
2. Don't skimp on your studies because you thought that by the end of 2012 it won't matter!
3. Remember that "I read on the internet that the world was going to end, so I didn't buy any Christmas presents" will sound really lame on Christmas morning.
4. This list could continue indefinitely...