I hammock (and am a woman).
It took me a couple nights to get used my hammock and learn how to get comfortable for sleeping. So your wife may just need a bit of trial and error.
As for specific techniques, I have a homemade hammock. What I do may not work for her. Still, I find that my most comfortable position tends to be half on my back and half on my side, kind of nestled against one of the hammock sides. This helps me keep a slight bend in my knees. I've never used a pad in my hammock or intentionally hung one end higher than the other. Playing with a ridgeline may help (I did a fair bit of tweaking on mine).