SOLVED. Fantasy (read in 2018/2019) -Girl goes to library and discovers a (man?) who helps her go into books. She can control creatures from the books after fighting them, and eventually captures a dragon who says he'd help her once. [s]

[Parker]

I cannot remember many details so some of them may be inaccurate. However she did capture creatures from books, and it was a series. She was placed with other people eventually, one of which who dies. There was a villain, although I cannot remember much about him. He was old I think? I don't know, I've been looking for a while :((

[Brenna]

Maybe The Forbidden Library by Django Wexler?

[Parker]

I think so actually! Oh my god, thank you so much!