hmm, unlocking sigil info is worse than finding some of those + and ++. sometimes they seem totally random and others you get by using a particular type of offering(didn't have any blitz or evasion ones until i used those moves more often).
i replaced thorns with frost bombs. set 4 up at entrance to an arena, and pop them while she's walking over them. after that hit her with everything you can: golem, skillful attack, blanet, eggs, more bombs.
try any high defense sigil you have, or any high health sigil.
i still need the carn. slime se++ if you want to team up on that a little later. i actually still need wyvern se++ too, but i'm not as interested in that.