It's possibly more complex than that? Maybe she was willing to work for less given other soft-factors; when she arrived, perhaps she found those soft-factors illusory (different boss; different project or work scope; coworkers aren't so fun after all, etc). In that case, asking for a raise is pretty reasonable.

Also, she may have simply gotten an offer she couldn't refuse from another company. You could argue that this shows poor ethics, but don't delude yourself, everyone has a price. She may have been generous asking her company to match.

Let's not judge people based on thin second-hand accounts.