Can I really be brought to small claims court?....?

I had a good friend who I asked to help me out 3x's a week. I told her I'd pay her $40 each week. The first two weeks (and the only two weeks) that she helped she only did 2 days a week instead of 3. We got into a fight when I quit my job because she felt that I didn't quit to her standards. She called me every name in the book and hared me for weeks. I eventually had to call Verizon and have her number blocked. I paid her $40 for the total of two weeks because she wasn't helping me the 3rd day of either week, I figured, why pay her more when the 3rd day didn't even come into account? She turned rash and started threatening to ruin my life, sue me, etc. for the remaining $40. I do not feel that she deserves the extra $40 because she didn't help me either of those days (I was a nanny and she was to watch the little boy for 2 hours on the days I needed help). I was paying her triple an hour what I was getting paid... the family I babysat told me that she should only be getting paid $20 a week, but she was a friend and I wanted to be nice. She then proceeded to har me more and tell me that she wanted $60 rather than the $40 that she claimed earlier. She is nowing giving me til May 13th to pay her the $40 (yes, I realize it is a small amount, but I don't feel that I owe it to her!). She has already slandered my name online--making up false accusations saying I am an "alcoholic" when I do not even drink. Not to mention, she owes both my husband and I money in the first place. For example we would buy her meals and she'd swear up and down that she would reimburse us and she never did. She hared me nonstop for days, text message after text message (I never replied). I do not want to get the police involved, I just don't want the drama. If she didn't help me on the 3rd day that we agreed to then why should I pay her for those days? It's $40--it'll cost her more to get a lawyer involved (which she is threatening she'll do). I think it's all talk and she is just trying to upset me, but I want to understand the laws and know what my rights are. I DID origionally say I'd pay her the other $40 just to get her off my back, but after she continued to har me for 6 hours one day, and I did the math of how much she was getting and the hours she helped me, I realized that she wasn't owed the extra money (had she worked the other 2 days she agreed upon I would pay her the extra $40). Is this something that could go to court? Over a measely $40? It sounds completely ridiclous to me. She hared me, she told me to die (yes, she did), and now she wants $40 more for work she didn't do!!