Magic Forums

So, I just had a long time client gave me a very low blow yesterday, and managed to get out of paying me the money she owes me of ~$300. It's a long story but over the past year she probably received a good hundred hours worth of free horse training for the horses I trained for her and now she's decided I owed her $350 so shes not going to pay me the $300 she owes me. I don't owe her $350, maybe $100 (work trade not cash). I woulda happily met her in the middle somewhere but she still would owe me about $200. It's a lot of money to me since I'm krazy broke myself right now and needed that money to help me get moved to be with my husband.
Anyway what I'm getting at, is there anyway I can assist Karma to alter her life like in "bad luck" ways and such without tipping my own karma 3 fold? My situation is too sensitive right now to take on bad karma for out right cursing and black magick. I have good karma over all. I treat others as I want to be treated, and I'm Charmed as it is (my life exists to bring happiness into others lives). But is there anyway to basically set her up to create her own bad happenings? Or simple things to inconvenience her life repeatedly maybe? She hurt me and I want to express on her without screwing myself and jeopardizing my happiness