I will tell the truth beside the barn there is a big tub about 30 gallons full of green stuff inside it and it doesn't look fresh to me It's been like that for over a year.My friend tells me that won't hurt her so I took the advice which was wrong.
Oh dear. This gets worse by the day. Your friend knows absolutely nothing, about animals or their care. Does he/she also have horses? Water buckets for horses and indeed all animals, should be cleaned regularly. Certainly after eating or grazing, many horses will drink or dunk their heads into their water and it will have bits of grass or hay floating. But I tend to think what you describe is very different.
You now also state your filly has an overbite. With this in mind, please do not breed her - ever. She is not breeding quality. I know earlier you had breeding in mind. Did the sellers explain this to you? Most owners of a decent stallion, would not breed to a mare with an overbite anyway. Misaligned teeth, can also make it difficult to eat and bit-fit, if you ever have her trained to ride.
I really hope you didn't pay much for this little filly. Are you in touch with her breeders at all? How did you come to find this filly? How did you ever already spend $50,000 on her? Thinking about the most expensive horse our family has ever owned, with the initial cost, pro training to ride and drive, the cost of a cart, harness and showing, feed, farrier etc., it still didn't end up anywhere near that much. I have a feeling, others might have been taking advantage of you.