I'm pretty sure she just gets extremely tired a spoiler somewhere explained it well but it's not going to do anything harmful...at least that is what someone said
it wont harm her dont be worried too much (づ￣ ³￣)づ
I read somewhere (a spoiler, I think?) that she can use it only once per day. In the manhwa itself, she said that she sleeps most of the day after using it. She also thinks that it's taking away her lifespan, since she is growing older faster, as you can probably see. She is still a child, yet she looks like a grown woman, much different than in the beginning of the manhwa.
In other words, she is shortening her life, but considering how young she died, she will still live much longer after she gets rid of all the pesky bugs around her.
she needs to slow down with it then i dont want her getting to old for the crown prince
I know it may sound stupid but what will happen if she uses that glass to much is it posable to use it to much