It reduces LH so it may be mildly estrogenic, but it increases FSH slightly so it can't be that estrogenic. The best theory I've seen is that it causes a rebound phenomena, where it suppresses LH initially but later on it bounces back. This kind of rebound can be expected after any brief androgen/estrogen exposure, such as one generally encounters on hormonal pulse therapy or short-term use of pituitary suppressive dopaminergics.
Regardless of how it works, I like the way I feel mentally on Angelica. unfortunately it only lasts a few weeks, then the benefits seem to stop no matter how I modify the regimen. I've never really received any libido effect though.