With the duplicates -- use your magic missile and / or scorching ray to hit each duplicate. The hag is fae (and oh so evil) so the protection from evil will protect you from hold person. Faerie fire will make it easier to hit. Use Lae'zels terrifying attack to keep her from casting other spells.
Create water will get rid of invisibility.
Yes, shoving works as does a pushing spell. A potion of hill giant strength will help there. But you miss out on some good stuff if you throw her into the pit.
And it might make it too easy but thief with dual daggers and Wyvern poison will end this fight in 2-3 rounds.
Other things that will help such as SH 'duplicity' spell.
