My dog is suddenly afraid to go outside at night?

hey guys, my dog is a year and a half old. she's a border collie golden retriever. she's been really good with everything as to be expected with her, but yesterday night I let her out for her last potty before bed and she bolted back inside quickly and proceeded to pee all over my kitchen floor. I thought maybe there was a snack or a sound that scared her so she ran back inside quickly and peed. but tonight she once again was to afraid to go out. she like stuck her head out and refused again. I went and checked the yard and found nothing wrong. closed her in the back yard with me and she refused to leave the door and was jumping up on it whining just wanting to go back inside.

she's fine during the day and seems perfectly fine outside normally. just after dark she's now terrified.

we have never left her outside all night and she's never been injured outside or anything.

we live in north carolina if that matters at all. she didn't have problems last year around this time.