@tamerlane If I'm remembering right, she said something in an earlier chapter to that effect. It's why she was already reformed after the first seal broke. As TVTropes would say, being stuck with literally nothing but your (effectively immortal) self for 100 year increments is "A Fate Worse Than Death".
@Satyam_SSJ10
The raws are posted to twitter first, then later on pixiv. The pixiv version sometimes combines chapters into one post. If you look you will see some of the pixiv posts are 8 pages long instead of 4 meaning those are 2 chapters at the same time.
@Tamerlane Let me try put it like this, do you know what it's like to swing your wings? What's the feeling charging yourself with electricity to function? Now can you tell if not knowing how or being able to do any of those have had a any impact on your life outside of share curiosity to experiment with them?
I think sleep is the same way for her, since she doesn't need to it and she doesn't understand what it's like. Likely that she spend her time either mulling over things she had done or meditating about things she would do once she got freed.