Depending on her age, low libido could be declining hormones. Testosterone begins to drop off in the 30’s, perimenopause can begin mid 30s, or any history of birth control can contribute. There’s also possibility of thyroid disorders, common in midlife women and will affect libido as well. For all of these things, finding proper care can be tricky because drs see anything in range as acceptable without taking symptoms into consideration.
As a woman who genuinely loves my husband, it made me feel like shit that the desire wasn’t there for me. I never regretted having sex, but I did wish a lot that I wanted it more often. (This wasn’t ever pressure or made to be an issue from him.) I’d always had a solid libido, but hormones and thyroid fucked me with zero warning. Hrt/trt was such an easy fix that it pisses me off to have gone years being told everything was fine.