To the people saying this is reasonable: Arm has a lot of options on how to defend the trademark that are not as wildly dickish as this, for example they could license the trademark to Azeria for this use, they could come up with a mutual process to transition her over to non-infringing branding in a way that was less disruptive to her work (and the benefit they get from it), or they could at least coordinate the whole mess with her internal contact to put a nicer face on it. Why they chose to go full lawyer hostile is not clear, probably they either don't care or are not internally well-coordinated enough to do better.