If a coworker reported a nother coworker sleeping to the supervisor and i just told her someone was?

in a patients bed not knowing why and she trys to make people think i am to blame for her getting into trouble when she's the one that reported her to a higher person how am i to blame espeially when others on the floor knew she was sleeping as well, even covering for her. why would this girl tell that i knew about it, which caused me to write a statement as to what i saw, when she told on her. if i didn't write something i was told the supervisor was going to write me up. there was another nurse on the floor covering for her saying she was off the clock, why not go home. who is really to blame here? i went to her and told her her that some people were being questioned and that i had nothing against her because i didn't report her, a few days leter she resigns saying that it's to many backstabbers there