"JoAnne65;c-16105849" wrote:
I must be doing something wrong :s Whenever I choose ‘add sim’, clicking on the alien in the list, all that happens is that I lose my own family members...
Are you adding her to an empty lot? I only suggested that because I thought it might be easier to save her to the household bin that way. 'Add Sim' should also work if you try adding her to the current household.
Or, you can try MC's Invite Over command. I think it's under Basic when clicking on a sim. Invite over the alien and once she arrives befriend (or use TCE to drag up the relationship bar), and use the 'Ask to move in' conversation topic. She should join the the household like normal (and bring along a Galaxa space car).