thanks hime!
as a clarification for the D skill, from what I have observed
The bonus damage for skills (or specifically her F) is calculated this way
The skill gives a passive 10/20/30/40 magic damage bonus as a base. The amount of bonus skill damage is just the percent multiplier times this number, so using her F skill would deal an additional 120 damage with level 4 of the first skill. When the D skill is activated, her base bonus damage doubles, so in effect all her percents also double, thus 240 bonus damage on her F.
As for the silence and the enemy girls under this effect taking additional damage, I don't think that's part of the skill. Her E skill seems to only last about a second. Is there any other interpretation of it?