So, it appears that you cannot confed Drycha, at least not through the improvement of Oak of Ages. This makes my teeth grit a bit. ME is a sandbox experience, so why not let you to confed Drycha when you reach level 5 on the Oak? She does not believe in the elves, but if you manage to finish the short campaign even she should see that you are not that bad for the forest.
His Royal Highness, Phoenix King Finubar!
"It has been too long since I drew a blade in anger, Tyrion. You have been my sword, and Teclis has been my shield. But now it is time I fought my own battles!"
I used to be crazycrix, then Epic happened and I became Dubinekdubajs, which I had to change again😀