Is she still on estrogen or was that a short-term medication years ago? If she hasn't had a checkup for a year or more, she could go in for one now and mention any issues dealing with estrogen and having no libido, as you describe, during that appointment. Of course, with any sexual activities, you need to entertain a good amount of foreplay with her that might trigger her libido.
Hormone therapy is a complicated affair.So she must consult urologist or gynecologist to understand the problem. I can suggest some exercises which may help her to normalize sexual system. Google, female deer exercise., kegel exercise, Anal peripheral prostate massage( this massage is applicable to woman also for this purpose.