It is ethical and expected for a journalist to obscure facts to protect their sources. It is unethical for a journalist to fabricate facts to protect their sources.

Also as someone with experience being anonymously quoted by journalist before, it seems to be standard practice for the journalist to defer any decisions on how they would like to be referred to the source. Odds are Evelyn is the one who decided to just go by Evelyn. She probably doesn't care too much about absolute anonymity, but she also wants plausible deniability.