Sorry, sometimes I can't stop myself. There's no way for us to know why your tort is acting that way. We might guess, but it would be just that, a guess. I lock my tortoises in at night. They share a tort shed that is separated down the middle. I have 2 Sulcata, one age unknown and the other about 8. Both male. Knobby takes himself to bed around 6:30, Big Sam spends his whole day snoozing under his basking light then about 6 pm he comes out and starts grazing. Sam takes himself to bed about 8 pm. Then I close both doggie doors and the larger people door, padlock them, and done for the day. I would never give one of my tortoises the opportunity to leave the tort shed at night. You might just close her in at night. A simple fix. Is she warm enuf at night?
I live in Houston, Texas. The weather here is warm to way to hot. She has a heated house with 3 radiant heat panels connected to a thermostat. Her house has a door put I have never closed it.
I went into her yard 10 minutes after the first time and she followed me to her house and went in.
That‘s her house in the upper right hand corner of the picture. We have 26 species of grasses and 5-10 species of weeds growing in her yard.
Rats or other critters moving around and making her uncomfortable.
The area in the pic is very well lit up. Might be too bright. Should be dark at night.
Your moving around might attract her attention and bring her out.
In any case, the door should be shut at night, as Yvonne said, to keep the tortoise in and everything else out. I go around every night, count all of mine, examine them, check their boxes and the temperatures, put them in if they aren't already in, and latch the doors shut. Then I open the doors every morning and they come out when they want.
I notice when koopa does things out of the ordinary as well. My Sulcata is goin on 7 yrs old, have had her for the last 2. November to March she puts herself inside her shed every night like clockwork and I shut her in. When temps are right in March I leave her door open. When it gets up to 90 after the sun goes down, koopa will sleep out in her enclosure on the grass or next to the wall. I soak her outdoor enclosure every night so her grass provides good humidity. I’m in Vegas, very very hot and dry here.
I read once on the Arizona tortoise compound site that there's have come out of their burrows with the full moon and stay out because it is so light, even to the point of freezing to death because high desert temps can drop significantly. I know my guy (about 100lbs, age unknown) will stay out all night if it has been too hot and not cooling off enough during the evening. So being summer I would say too hot or too light but who really knows!!