Unfortunately DS is a good sleeper so it's hard to help but if he doesn't respond to that I assume that something else is wrong - nappy, hungry, thirsty etc or in pain. So I then go through all those eliminations if baby go nigh nigh doesn't help. Sometimes I realise he expects to be picked up so I don't let him develop that habit if there is nothing physically wrong. I also try to wait at least 15 mins before I go in there and the same when I walk out.
I think if you are consistently having sleep problems though it's an emotional need. Sleeping next to the cot allows you to feel better because you know she knows you are there, but at the same time not developing that habit of taking her out of the cot.
On night lights I have read a lot of positive things that it actually helps with anxiety. I bought DS a gimmo nightlight that he can have in the cot with him for when we stop using the baby monitor we have that has a nightlight as part of it. Had to take gimmo out of the room for now though - he knows he can hold it so HAS to have it in the cot if he can see it! It's a major comfort to him whoops. Instead we have a normal night light and muslin face cloths as comforters.