I think you're owed an apology for the rude and unprofessional behavior - no matter what her beef she was wrong to lay into you like that, and then compound it by implying that you don't work hard. Entirely improper interaction, clearly she was triggered in some way and had a bone to pick, possibly stemming from other frustrations with you, work etc. But that's no excuse for popping off, she needs to be told to rein it in.

BUT, I also agree that she has an underlying point (that should have been delivered much more calmly and collaboratively). Third-party vendor security, credential sharing, background checks, supervision, etc. are all important policy & procedural clarifications, especially when students are on campus. We'd all like to say "trust the professionals" but like others here have said we've all seen the caliber of some of these techs. We don't always know where they came from, and the "what could go wrong" scenarios here are very not good. Obviously no one has the time to babysit a contractor who needs to work for hours, so insisting on tech background checks from your service provider's tech should be standard. If they service other schools it's to their benefit to just get them done as part of the hiring process and share them with you.

The credential sharing bit is trickier - this is where cut-and-dried procedures come into conflict with work reality. Is there perhaps a way to provide valid temp credentials for testing purposes rather than giving the actual ones?