Thank you!
She is indeed starting from scratch every night - she builds a lovely new web, by the end of the night it's a wreck from her catch, and presumably she retreats with her food to a hideaway for the day before doing it all again. (Though she may be gone - last night all we saw was the beginnings of the upper frame. She may have been a victim of her own success, as she'd gotten so large she was probably easy for predators to spot!)