Would you "tattletale?"

Short version: would you tell your grad school professor that a student had been cheating on exams?

So, this might be a kind of juvenile question, but I am conflicted and am looking for some unbiased opinions! I am a grad student studying speech-language pathology and I love what I do! I, along with (the majority of) my cohort work so hard to get good grades and provide excellent care for our clients. We had a test yesterday that many of us spent weeks studying for. As I was getting up to turn in my test, I noticed a classmate with the study guide pulled up on her phone. Apparently another girl saw it as well. Now, I don't want to be a "rat" and I know the saying "snitches get stitches," but this girl plays games on her iPad during every class and doesn't seem to pay much attention to lectures. On top of that, ANOTHER student said they saw her doing the same thing during a different test. We are wondering if we should tell the professors or if we should keep our mouths shut. What would you do?

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