You have to dress her properly like one of the dialogues says. But you're probably refering to a special dialogue that you need to trigger before you are given the option to go out with her.I don't know exactly how but it has to do with talking and playing with the bot constantly and maybe do her the pium pium like Naikalo said haha. Just try that and eventually,when choosing "talk", it will give an option that says something like "I need to talk to her about the posibility of going outside". After that when clicking the door you'll have the option and if the bot is missing something it will tell you. She also needs all limbs of course
Edit: Forgot to mention,I'm not entirely sure but I think you actually need to go to the store one or two times more after she asks you to see the bot