During the fight she summons adds called "explosive device". They hit hard but can be mezzed. After we finished Tilda, we began killing the adds, and at some point each of them cast "Shrapnel", which the spell info says is a 19K AE, tho it did "only" 15770 to me. Two of them took out my monk and some of the healer mercs, but our pally and enchanter finished the job.
Tilda dropped Grintwisdom's Shawl and Celestrium Encrusted Carpal Clay.