How much does party xp multiply by?

Just wondering, because I am trying to figure out if there is a point of getting my GF into this game. We're gonna be playing SWTOR. However, no point in her putting 10 days into this if there's no reason to come back...and if the xp is just split 50/50 the grind would just be stupid hard.

1. kill a mob
2. check the xp gain

1a. form a party
2a. kill the same mob
3a. check both of you exp gains and sum them

voila

with duo its +10% exp that is shared.
http://legacy.lineage2.com/news/highfive_06.html

edit (whoops read wrong column)

Hmm, that list is outdated since max party size now is 7..

Unless the xp ratio didnt get changed