I think that she was sent in to check the place out... How is it gaurded. Is it gaurded? How many weapons do they have now? What is their location? Is there confusion among the group? Who is leading?

If you want to wage a war on people you gather intelligence about them and the current situation.. This would be my guess as to why she is there..

__________________
Please don't give up, Des. Because all we really need to survive is one person who truly loves us. And you have her. I will wait for
you. Always. I love you, Pen

DESMOND: I love you, Penny. I've always loved you. I'm so sorry. I love you!
PENNY: I love you too.
DESMOND: I don't know where I am, but--
PENNY: I'll find you, Des--
DESMOND: --I promise--
PENNY: --no matter what--
DESMOND: --I'll come back to you--
PENNY: --I won't give up--
BOTH: I promise. I love you.