Why won't my dog come in the house at night?

My dog, Charlee, is 1/2 golden and the other complete mix, refuses to come in the house at night. During the day, on the weekends, she comes and goes as she pleases . During the week I work full time and my husband is home 3 days a week. When he is home with her she rarely spends her time in the house, then I come home she will come in for a bit then eats and goes back out. Around 9-10 pm I call her to come in the house. Most nights I have to coax her in the house with a treat other nights I will call her several times with a 10 or so minutes in between and then finally she will come in. I can't figure out what the problem is as there isn't really a pattern. We love her and she loves us but certainly doesn't sound like it. She is loved by our neighbors and has a lot of energy. I walk her as often as possible and we play with her in and outside the house. I am hoping someone can help us with this situation.