There are " morning after " remedies for animals but the options only cover short time periods after the female has ben impregnated. I would call the SCPA, or local Vetrenarian to find out what is available and costs. The SCPA can help with low cost alternatives. You will have to call now as time is of the essence. Good luck to you. Spaying and neutering are always the best choices.
Take her to a vet as soon as possible.
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