Could be a fluctuation in hormones related to menopause. Hopefully someone with more experience will confirm. It might also be that she's finally figured out what makes her happy and comfortable in the bedroom. For women, so much of their enjoyment can be affected by what's going on in their head. Maybe after 45 years, she's finally learned to relax and just enjoy herself!
You said it all slow_healer. I am the same way. My sex drive kind of took the 30's off but once I turned 45, things got moving very nicely.