If one recruiting firm won't represent you as a candidate, it's no loss, as there are thousands more that will - and recruiting firms aren't comparing notes with other firms on who took a counteroffer.
It's a threat that is totally unrealistic.
As a recruiter, I'd actually say that technologists are more likely to be able to damage a recruiter's career than the other way around. If word gets out about a recruiter not behaving properly, that word can travel much faster in the worker space than word travels in the recruiter space.
If she actually thought that was tantamount to "you'll never work in this town again", she needs a reality check. Oh, this one recruiter firm won't work with me, whatever will I do?
I've worked at four different companies. In order, I got those jobs through Craigslist (2007), Monster (2012), Indeed (2014), and a friend referral (2016). None of them involved recruiters. Also, during the times I've been looking, I talked to a very large number of recruiters. If one of them blackballed me, it wouldn't affect me because I talked to so many other recruiting firms, and even then I ended up getting all my jobs without them.