I think INFP, based on numerous interviews and her art (especially her lyrics). Overall, I get an impression of abstract Feeling (Fi) and concrete iNtuition (Ne) rather than NiFe. Her style of expression seems so different from most INFJ musicians; her imagination seems expansive, whimsical, and pulling things in from a hundred different directions, playing off of them and making them uniquely hers by processing them through Fi and giving them vibrant and idiosyncratic emotional color. INFJ imagination is more heavily abstracted/removed from its input, and in my experience comes across as less whimsical and playful and more focused and intense. The links from external input to internal vision are much harder to trace.
I also think she's a 4w3 with a 497 trifix.
I definitely see 4w3 for Enneagram, her music has the e-4 themes throughout it... envy, yearning, creating one's inner world. INFJ's are more intense and focused, and there's a feeling of structure and order to INxJ music as a whole. Kate's work is more spontaneous, expansive, and whimsical, which is more indicative of IxFP preference than INFJ. It's a contrast from the e-4 emotionality that you get from Muse, which is more INFJ influenced, and there's more intensity. Kate's most intense piece is Waking the Witch, but even then, the way the piece is constructed with different samples of voices, to the way the music takes its form, it still has that light and airy IxFP vibe. You'll find that INFJ music tends to have a focus not only on people, but also some overarching idea, web of concepts, connecting people to the universe, cosmos, and how we all play a role within this massive web and how we could avert natural disasters (ex. Muse's song Unsustainable). Kate's music is more fluid and dreamy. She may seem INFJ-ish on the videos, but in a way, she also reminds me of Luna Lovegood from Harry Potter, who is INFP. It's also in a similar headspace as Peter Gabriel's music, which from reading about him, he comes across as an INFP, same spontaneity. Kate Bush takes an insanely slow (slower than Peter Gabriel does!) amount of time to create her music, perfecting it, taking her time, and that's more indicative of Perception, rather than Judging. It's a part of collecting all information to make a decision, rather than arriving on a decision quickly like Judging types.