Scared of the dark?

It seems like Ana doesn't like to go pee outside when it's dark. Is that possible? Even if I turn the outside light on (which is quite bright), she's still really hesitant to go. She'll go if I go out with her, but she'll run right back in after a few minutes. It's making house breaking a little more difficult.

I assume just taking her out every night will help her get used to it, but I'm just curious if anyone elses dogs have done this.

Edit: I should mention she's 9 weeks old and she's not scared at all during the day.