The new girl gets more ...

It depends on what sort of contract you are on (indivdual or collective). Its not uncommon though. Does she have more experience / qualifications than you? (no offense)

If you are really seriously peeved then you could try talking to your boss, but given salarys are supposed to be confidential then it could make you look bad.

Before doing anything that may not work in your best interests, best to find out about her.

I was recently offered a job & the rate was lower than I was used to in that field so they up it by a huge amount which would of been on par with people that had been there years. I have been in that field years & have done several courses, so I consider myself worth top dollar.

So she may have a very good contract, I am surprised that her earnings are common knowledge as they usually try & keep this stuff quiet to avoid staff issues.

We had similar "issues" at work.
The crux of the matter is they are called "Individual employment contracts" for a reason.

To be quite blunt, what is in her employment contract is none of yours or anyone elses business.
What she has negotiated is meant to be private between her and your boss.
She may have more she is able to bring to the table, she must be worth the extra money.

If you are steamed, either negotiate a payrise for yourself, selling yourself and what you bring to the firm. Bringing up her pay rate is going to get your bosses back up, because like I mentioned earlier, its between them.

If it bothers you that much, I''d look for something else.