Sue

If she did not pay you according to an agreement, you could sue her in small claims court. However, you would have to pay a filing fee for your suit and the cost of having her served with the paperwork.

If I understand correctly (punctuation helps!), you worked for a week at twenty dollars per day. That means you would be suing for around a hundred dollars. It would cost you about fifty dollars in costs to get the suit started, which she would be ordered to reimburse if you won, but that could take a while. It is also one thing to win a lawsuit and another to get the other guy to pay the judgment ordered by the court.

The philosopher Voltaire wrote, "I was only ruined but twice: once when I lost a lawsuit, and once when I won one." He said it hundreds of years ago, but his point is still just as valid today: suing somebody is almost as stressful as getting sued for yourself. It probably isn't worth the time, money and aggravation to sue somebody for a hundred bucks.

Please understand that this is a general discussion based on California law and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like Avvo, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.