Technically, by Homeopathy Principles, This Should Make Her Infertile
Yes, homeopathy is just a glorified version of the placebo effect, but even if you’re just making fun of the practitioners, you should at least get the basics right. For Homeopaths, you use really small bits of stuff that, in larger amounts, would cause the symptom you are trying to AVOID. The idea is to get your body to trigger an immune response that has nowhere to go but to whatever is causing the problem that you are resorting to homeopathy for.
Getting your body to trigger an immune response to semen is NOT a good way to get pregnant.