What can lower a woman's testosterone levels?

Many options. Options to lower a woman's testosterone include, but are not limited to, oral contraceptives, spironolactone & eflornithine. Of course, correcting the cause is the ideal & preferred method given adrenal or ovarian tumors, etc. And of course, if your partner is taking topical/transdermal testosterone, be sure to give him enough time for it to dry before making contact to minimize transfer risk.