Kelly - plenty of lesbian posters on these boards, no need to be defensive.
You're right - Premarin won't likely do anything for her sex drive. You might try to approach her on the general issue of bioidentical hormone replacement, as it is likely more appropriate for humans to use hormones that are the same as what our bodies make, rather than synthetic compounds and horse estrogens.
Still - the bigger problem here is hat she doesn't SEE her loss of libido as a problem. I went through a period of decreased libido. I went to my doctor to find out what was the matter, because previously I had loved sex with my husband. If she doesn't care enough about your R and about her sex life to look for answers, then maybe she's not the one for you?