Can instructors regrade assignments WITHOUT the student putting in a request to do so?

For context: In February I had been given an extension on a lab report, submitted within that time and got my marks back- no issue. Then two weeks ago I was emailing the lab coordinator about a quiz mark being entered wrong, and when she went into Qurceus to change the quiz mark she also went back to the lab report from a month ago and deducted 20% as a late penalty. I assumed this a mistake and I asked her about it, but we then went back and forth about it for the next two weeks (she basically just dodged the question every time I asked).

This morning she asked for proof that I had been given an extension, I gave it to her (literally just forwarded her own email back) and she removed the late penalty BUT also regraded my assignment so it was almost 10% lower than I had originally scored. Today this whole exchange happened in course of like 10 mins so I honestly doubt she even re-read my assignment, but aside from that is this even allowed?? I know students can ask for a regrade but even then we're warned that the mark could go up or down so we should really think carefully about it. I didn't even ask for a regrade here she has just gone out of her way to do so and now says there's nothing I can do about it.

edit: I know that profs can grade/regrade stuff obviously, but don't they have to give a reason? this coordinator has given no reason and basically refuses to give me one. I'm just frustrated b/c it feels like they are pissed I pointed out their mistake and now are docking pts. maybe im just biased rn