I know your birds spend a lot of time out of the cage, but if it's possible for you to keep her in the cage for a while you'll be able to tell when she lays an egg. If she's out of the cage she could drop it just about anywhere and you might not ever find it.

can they hold the egg inside when it's ready if they think the moment is bad or they don't find a good place? Or is it something that they can't control too well and when it's ready they have to pass it out?
I came home a bit prior their bed time. She looked OK. She flew to the top of the fridge and sat there, and I thought maybe she would lay it at the same spot, so I got all other birds in the cage in the living room. I decided to give her some quiet time on her own. Some time later she flew into the living room and saw that everyone was in the cage. It didn't take her long at all to get into the cage on her own. I rolled them all to the bedroom and now the light is off... can she drop it at night?
I worry that she needs to pass it out but she didn't, and now it's dark. IS there a possibility?

I would think that it's a lot like giving birth to a human baby - there's really not too much you can do to hold it back! It's possible that she won't even lay another egg, since she didn't pay any attention to the one she already laid. She may not be too committed to the egg laying process and that nesting area has already been disrupted. It'll be good if she's already finished, but it's possible that she might lay more on an irregular schedule. If she gets egg bound you'll be able to see that she's in distress, so keep an eye on her to make sure that she's acting normal.

from having child birth experience, I remember I didn't have a huge desire to get her out, I would rather go to sleep LOL

she laid another egg today (her schedule mush have shifted a little), at the location that I was suspecting would be her next choice. what was different is that this time she was surrounded by everybody else. When the egg was laid, other birds (her children) got very excited. Again, she was not protective of it. I had to remove a whole thing including the egg (I altered the whole area) because I was afraid of what kids could do to that egg (or get inspired)

Birds who don't have their own eggs can get very excited when they find an egg, so you had the right instincts about keeping the egg away from the children.