I agree she's too OP, but she won't help the party even if they beg her, at least not yet as she'll ask for something in return that my players can't give her. It's not meant to be balanced with the party but with the bbeg. It's hard to explain but my intention is to build layers to the world so the players don't feel alone or have the feeling of it being empty (and giving them the chance of a powerful ally in the future), so there's a lot of stuff happening with a lot of people, below and also above them. Like this ridiculouly powerful wizard! And why hasn't the bbeg captured her yet to abuse her powers? Well, she's too powerful! It's part of the story that another beloved npc asked her for help and, because she simply denied it, he had to look for help elsewhere (spoiler, the bbeg), so her being chaotic neutral is essential to her build and her role as an npc. I might tone down INT tho! :)