When silver transforms to wolf form witchmail only decreases the ult cooldown but the cooldown only starts after her ult is over and she's back in human form which makes witchmail useless on her in wolf form, it has been a bug since silver's release I believe
I believe Silver's Lycans Curse operates similarly to other channeled abilities whereby it isn't off cooldown, as it's being actively channeled and as such wouldn't be affected by activated cooldown reducing effects.