Can I bring a person to court over a personal loan?

I made a pretty dumb decision and lent a close friend 7000 dollars. I gave her a while to pay it off, well here we are 4-5 months later and she keeps telling me that she is going to pay me and continues to make up excuses. However I did make her go get a notarized letter which states as follows, "Payment to one (John Doe) in the amount of 7,150 dollars from one Miss (Jane Doe) is to be paid no latter then March, 1st 2007. If payment is not received by on or before that date legal action may be taken" And it is signed by her and it has the notary stamp. My question is regardless of how she spend the money which she did pretty foolishly, am I legally entitled to recover my money in a court of law?