My Party;
Level 4 Elf Wizard (Abjuration)
Level 4 Halfling Fighter (Kukri TWF)
Level 3 Human Cleric (Sarenrae - Good Domain)
They've also been dragging Shalelu around with them as much as they can. They are pretty new to Pathfinder, so I've been going a little easy on them, but they also have had some good luck (they managed to kill Erylium by complete accident, with no preparation, first turn), so I want to give them a good scare this session!
So my party has been going through Rise of the Rune-Lords, and have arrived at the Nualia boss fight. They snuck in through the tentamort cave on the side of Thistletop, and in order - Killed Bruthazumus (before he could raise the alarm), turned Orik, and kidnapped Lyrie. Then, tired out from the fighting, they climbed out and returned to Sandpoint. The next day, they infiltrated Thistletop again, this time sneaking past a couple of goblin patrols and heading to the bottom floor. They brought along Orik and Shalelu for this part, although Orik has been reduced to ~16 Hp by the trap (they had him take the lead, and I thought I remembered he didn't like going downstairs, so I decreed he didn't know about the trap).
They caused a lot of noise to draw out Nualia, but she sent out her hound to investigate - they ambushed it and killed it before it could bark, but she knew when it didn't come back that it had been killed, so she cast her buff spells and waited for the enemy to show up. Eventually, the party crept up to her room and burst in, and that's where we called it for the session.
My question is, how do I make this fight satisfying for the group? Nualia, even buffed, only attacks twice a turn, and she hits pretty hard, but the party has a good amount of healing and managed to get to her without using much of their resources - I'm worried they'll steamroll her. I suspect the party is going to try to talk to her to find out her motivations - I plan for her to talk long enough to get a feel for their abilities and make a plan, and then she'll attack them while they're on the backfoot. I have also toyed with the idea of her executing Orik "cutscene" style, to frighten the players and simplify the battle. I've also considered some backup showing up if the fight doesn't go her way - the party made a lot of noise, so some goblins or the yeth hounds from upstairs might come down to her rescue. Alternatively, I have considered her focusing on escaping using her spells and abilities, and having the party confront her later during Skinsaw Murders (maybe she breaks Tsuto out of prison before his hanging).
Ultimately, I just don't know what's the best approach; I don't want her to die unceremoniously (after all, the party managed to sneak past the first floor of Thistletop, so I want them to really earn this win), but I also don't want her to wipe the party, or bail without a fight and cheat the party of their confrontation. Does anyone have any advice or suggestions? I'm open to any ideas.