You can speak to Mission after she joins your party outside the Outcast village gate in the Undercity on Taris. If you don't speak to her, you may be prompted to do so when she's in your party (although this can be ignored).
This is as far as this dialog can advance before leaving Taris, at which point you need to speak to her briefly about what happened there first:
Now you can talk to her about her brother again:
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She repeats this last line whenever you try to talk to her about her brother again before meeting his old girlfriend, Lena.
Mission's Brother
After the last dialog, Lena can approach you upon entering or exiting the Ebon Hawk on Dantooine with Mission in your party:
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If you talk to her about her brother again afterwards:
The next time you speak to her about her brother, she's been doing some thinking:
Template:KotOR Dialog
She repeats this last line whenever you try to talk to her about her brother again. Next stop: the Czerka office on Tatooine..?
Party
Mission may speak to other party members.
Bastila
Carth
Zaalbar
