to be honest, i think there's a balance that you've obtained. first off, i'll tackle the first question. it's not co-dependency if you can be fine during the day regardless of whether or not another person is around you to help you. i personally don't think it's you avoiding your problems OR using a healthy coping mechanism.

now the night-time thing. i notice that (minus all the really bad traumatic things that might happen during the day), most people tend to cut in the late evening forward. i believe it comes down to the chemicals in the body being switched from "i'm going to be active" mode to "i'm going to start slowing down for rest". there are meds that are quite easy to obtain from a doctor that can help treat both the anxiety and urges that you deal with upon entering nighttime, as well as help you remain asleep. it might be something to look into

It's healthy to stay around people when you're feeling like this! Everyone is always telling me not to be alone when I feel down.
Good job on using that coping mechanism :)

I don't know what it is, but I get worse at night too. But I think it's awesome that you can help yourself by remaining around ohers, it is hard to do sometimes when you feel low, at least for me anyway.

keep your head up! it'll be okay!

Codependency is where you obsess over the person and constantly invade their space and time with yourself, and if he doesn't respond the way you want you overreact. You are not because you are just feeling lonely at night because the night is when your vitamin D is lower because of the sun being gone which lowers brain function to be positive. You are alone feeling at night, but you are never alone because there is always ways for you to get to something to bring you up. Never let yourself be alone, even if it means walkin to somewhere to be around even a crowd can make the difference. You have a community here, we won't let you fall on your face. We love you, I'll be praying for you to feel comfort at night.

I don't think it's a dependency issue, as you said yourself you're okay during the day on your own just at night it starts. In a way I get you if this is going to make any sense at all, night is dark and generally the dark is associated with hopelessness because there's no light, no hope almost. But then you have to remember the sun always comes back eventually :) Especially being on you're own at night after what I just described you know.