OK I get it. Your girl mated 21 days ago, and now she is passing blood with clots. You wonder if she is miscarrying? (spontaneous abortion)
It is likely yes.
Ghilly gave you some splendid advice. Get her to a vet NOW. Don't wait. She could be in trouble. It sounds like she is.
She may need to be spayed. Prepare yourself for that.
I am very sorry, but would you please re-post this? I'm afraid that I don't understand what you are asking here. We cannot attempt to give you any kind of answer until you make the question understandable.
From what you have written the only thing I can say is get her to a vet TODAY to have her examined. Don't wait, if she is passing clots she could hemorrhage and lose a lot of blood. She needs to be looked at NOW.
Ghilly