Talk:Grounders/Trikru/@comment-26247132-20150504213005/@comment-26223363-20150505080626

Not sure if this would be enough info, but in 2x09 Marcus calls Lexa "Lexa kom trikru" Stating that she is "of the Tree People"

Before she became Commander of The 12 she had to be apart of one of the Clans, being Anya's second makes the most sense for her being Trikru.

Also when Costia was taken The Ice Nation and The Woods Clan were at war. They wanted info on Lexa so they took Costia.