Enough with the semantic arguments:
1. Calling a servant an "au pair" or a "perk" doesn't make her less of a human being.
2. ALL human beings have rights, and in the US those rights include employment protections, such as a minimum wage.
3. It doesn't matter what "perks" the diplomat was promised. She cannot violate another's legal rights because she feels entitled to a servant (excuse me, an "au pair").
4. Shipping a human being overseas to be a servant with the expectation that they will be underpaid doesn't make this okay. On the contrary, that's ominously close to human trafficking.
5. Asking to be released from unjust and illegal labor conditions and proposing a settlement for back-pay and damages IS NOT BLACKMAIL! (If it were blackmail, why is the servant not being prosecuted for extortion? Answer: because it's not blackmail!)
6. The arrest really isn't about the servant (Ms. Richard). Ms. Khobragade is being prosecuted by the federal government for a crime committed against the federal government. She lied on a federal form, which is a felony right there. She also did so to cover up that she violated the minimum wage law. That's why she was arrested.
7. All the talk about servants that has arisen in Western media and online is due to India's response and how stunned we in the West are that there are still people on this planet who can be this inhumane (as your comment sadly illustrates).
Edit: Grammar fixes.