J.C.
Yikes. Unless you plan to breed her, you must always "fix" your dogs and cats. It will def cut down on the humping. It may also help to get her a stuffed animal she can hump. Whenever she humps your leg, tell her no and give her the stuffed animal. Train her to only hump the stuffed animal. But yes, you should definitely get her fixed. With all the stray and abandoned animals, it's almost a requirement these days. Even breeders sell their dogs on a "nueter contract" meaning it's a requirement that you get them fixed by the time they are 1 year old. They won't send you the papers until you do so.
There are places out there that offer free or low cost nueter and spaying.
Spay Neuter Your Pet (SNYP)
PO Box 29435
Dallas, TX 75229
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Discount certificates for pet spay/neuter in the Dallas-Fort Worth area.
Luv A Pet S/N CLinic South Oak Cliff Dallas TX
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HSUS Spay - Neuter Clinic/Animal Wellness Center
4830 Village Fair Drive
Dallas, TX
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SPCA of Texas
Martin Spay/Neuter Clinic
Dallas, TX
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Low cost spay/neuter. Also, for pets of qualified low income people, there are low cost veterinary services.