how do i even rescue mitzi
You rescue her on the Tarkus mission in the same location where you fight the pirates and disarm the bomb. If your like me and you have already long finished with the mission, there are two ways to get her; save edit, or the cheat.
Cheat: Simply type in mitzi during gameplay.
Save Edit: Open up a save editor; remove flags, tarkus bomb timer, met ugc trooper and stellar tether closed entries.
You can recruit her if you did the normal way 8-10 days after the mission at Tavros in the ship bay. Whereas the cheat it can go either way being immediately, or the 8-10 days time for her to appear. Remember to make saves in case of errors or bugs.
Hope that helps