most people moan when their snake is inactive

By definition Cornsnakes are diurnal, so both active night and day. You don't mention its age or sex, but it is the breeding season for cornsnakes which might explain the increase in activity.

 

The OP does say 'her' twice and 'she' once, to be fair :whistling2:

Unless the set-up is massively cocked up and the snake is desperately trying to get away from excessive heat or moisture or something, this is nothing to worry about for a corn.

Once settled in they usually chill out very well, lose all fear, and can be seen at random intervals at almost any time.

Is it still feeding?

 

She is just over 2.5 years old (she was in December, her birthday is June 6th)
I was always told they were nocturnal, which is why I thought she'd be hidden during the day, and active at night.


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I was always told they were nocturnal, which is why I thought she'd be hidden during the day, and active at night.

Normal indication of a snake that is nocturnal is a vertical pupil like a cats. Corns have round pupils, normally associated with daytime activity.

Having said that, snakes that are normally nocturnal can be active in daylight hours and vice-versa

 

Mine is out in the evening and night. I RARELY see her out in the day. She is about 5 months old. But I can always count on her out and about at night.

 

Same with my corn, the only times I don't see her at night is after she'd been fed, or if she's going to shed.