Well, we are guessing, but you are using your super power of evasion.
I think that the Bear knows her and she will provide some special training and help. It is also possible that she could have a background similar to the Bear in that she tried to affect change for the poorer people outside of Mystrock, but she could not succeed on her own. Marine has the gift of bringing people together for common purpose and she genuinely cares about people too. Those are both great traits in a leader even thought she is very young.