By the way if you defeat Valenna first, then her dog will turn neutral and stop attacking you. Also rangers can learn the skill to silence their target.
You can also cast teleportation to Valenna and drop her in-front of Madora, so Madora can knock and pin her down. After that cast midnight oil around Valenna or chill her to prevent her from escaping.
If you're not able to stop Valenna from summoning, then you could try charming the summoned creature (I don't know if this work for summoned creatures).
For me, I just constantly use the touch skills, e.g. lightning / freezing / burning touch.
