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I am assuming that you mean a discharge from her vulva (vagina). If she was spayed more than a year ago, and has had no problems since then, there are a few possibilities. One is that she has a urinary tract infection and there is a little blood (from bloody urine) that is staying behind on the outside. To check this out, you should wipe off this area with a damp towel or baby wipe, and then collect a fresh urine specimen (in a plate, bowl, jar cap, etc. and take it to your vet for analysis. Another possibility is that she has hair around her vulva, and it is trapping urine, skin cells, and moisture, which looks brown as it dries. It may even set up a dermatitis of the skin in that area, but if this were the case, I would probably expect her to try to lick herself. Occasionally a spayed female will get a vaginal infection, but this is rare and might suggest a hormone imbalance. What I would suggest, if it is not a urinary tract infection or a "personal hygeine" problem, is to have your vet do a thorough exam, to make sure that somethig odd is not going on.
I hope this helps. Please let me know if you have any more questions.