An attempt at redecorating? Who knows? But to assume she did it just because of you just makes no sense at all.

I do think you really, really have to talk to her about how triggering the furniture placement is for you. Perhaps if it's physically possible in the room to move the chair forward, she'll let you slide it forward when you come in. I'm sure she will be willing to hear you and search for a solution. Remember how relieved you were when you asked her to schedule you on a different day? She heard you and was able to help you with that.

I wonder if the meanness you perceived has much more to do with your mother - probably triggered by feeling punished in that chair- than it has to do with your T?