Shadow and Carlotta

http://wiki.guildwars.com/wiki/Shadow

I exited temple of the ages, and within a minute or so of traveling I noticed that Shadow and Carlotta were in my party as allies, but I don't know how or when they joined my party. I don't have any of the two quests active in the wiki involving her.

Any ideas how this happened? Is this a random thing? Thanks.

if you have completed either eye of the north or the prophecies campaign, someone of the shining blade group will appear when you enter areas in kryta:

http://wiki.guildwars.com/wiki/War_in_kryta

jump down to the allies and escorts sections and you will see this.