The time doesn't matter, all you have to do is enable RNG and give her more than one medium-level mission that involves a dildo or a vibrator, and then new images of her will appear. To know if you triggered it, she will say these lines:
1° "W-Wait, you're giving me this? I-I don't know what to say"
2° "Thank you... I guess I'll find a use for it later"
3° "U-Um... Thank you for the help and all..."
4° "I-I'll see you later, okay? T-Take care..."
After she finishes speaking, our POV will notice that Amanda seems a little distracted while waving goodbye. At this point, the option to follow her or not will appear. When we follow her, we will appear in a corridor where there are also two options: to peek or not. After that, have fun with what you will see behind the door.
I realized it had nothing to do with leaving the lab; it was just handing her medium-level missions that triggered it.