I got a second cat six months ago and my resident cat still hates her. Is this fixable?

Six months with no resolution is genuinely hard, and I want to say first that you did the right things. The slow introduction you described is exactly what should happen, and the fact that they can now be in the same room without physical contact is actually progress, even if it does not feel like it right now.

What you are describing, with your resident cat consistently chasing and the new cat spending most of her time hiding, tells me the social dynamic has settled into a pattern that the cats now consider normal. Your resident cat has learned that the chasing works. The new cat has learned that hiding is the safest strategy. Both are stuck in roles that are now self-reinforcing.

The question is not whether this is fixable because in most cases it is. The question is what specifically needs to shift to break the pattern. That usually involves looking at how resources are distributed in the space, whether there are enough escape routes and high spots for the new cat to feel genuinely safe, and whether there is a way to rebuild neutral associations between them through structured positive moments rather than just coexistence. Six months in, I would recommend doing a full assessment of the space and the relationship rather than trying individual tweaks, because at this point you need a clear picture of what is driving the dynamic. The Work With Me page is the right step here if you want that kind of detailed, specific support.