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from what i see, it's that mirabel's main gift was her relationship with casita (in general it was that she connects the gifts/miracle with her family).
i don't really remember if we did see how others communicate with casita, but we see A LOT of mirabel conversations with casita. her asking if casita can help in bruno’s room, asking how she’s going to safe the miracle, and definitely the whole asking casita to help her to get the candle and how in the process camilo and isabela didn't get it because casita was busy helping mirabel?Â
so what i see from her ceremony wasn’t that her door vanishing, but blending with casita. her door was the door that open casita itself, as it shows in the end. if i go with the interpretation that each room resembled "their world", mirabel's door, which is casita's main door, lead to her world, her family, the madrigal family. that's my take i guess?
