((I guess this is an important question, and since I don’t like reblogging my own stuff, and it doesn’t make a great ask on its own, let’s answer it this way!
First, Pinkie Tai and Bedlam have a shared canon. True, Pinkie Tai basically treats all canons as part of her own (even if they don’t reciprocate) due to meta multiverse weirdness, but these two are basically inseperably intertwined as far as history goes.
In essence, Pinkie Tai and Bedlam originate from the same version of Equestria, and maybe a few other blogs that have interacted with her heavily (e.g. Trixingno, Spades, Phonez (alas, no longer with us), maybe Bad Bloom), though not necessarily. Pinkie Tai herself doesn’t distinguish between universes (except for Loki jokes), and has no problem with the concept of having multiple Twilights or whatever running around. Pinkie Tai views all realities as part of her own, even if they contradict each other. She’s special like that.
Secondly, when the Master Key story arc kind of petered out without resolution, I basically decanonised the rubber thing for Pinkie Tai, mostly because I didn’t want to draw that much shiny all the time. Especially for her hair~
However! The events did take place as seen, even if we never see a conclusion to it. Due to the Hiatus spell that’s been mentioned a couple times way back, it still gets folded into her canon. The way I consider it now is that the rubber spell worked, but it’s only available as a super mode. Pinkie Tai can transform into a rubber pony as she needs to by drinking a certain soda (it’s an Elongated Man homage/ripoff!) and temporarily transform. She just doesn’t do it much, though, since this isn’t a blog with a lot of action scenes. Now, put her in Acetic Rarity or Hot-Blooded Pinkie’s universe, though…
And that’s my headcanon on how all that turned out! If you ask the right questions, I can totally canonise all that, too! Eventually!))