As a long time and thank God Ex-Headhunter, take her call. Yes, she's an unprofessional hack, but most agreements between companies and agencies stipulate that if a resume has been sent over from the agency within the last 6-12 months, the agency gets the referral. She can influence the hiring process.
When I started, it was a noble profession, what has happened is the hiring model has changed. Twenty years ago, you could pay a draw to a headhunter that was respectable enough to earn a living. As salaries have gone up, draw haven't. So what you get are fresh grads, (who have no credibility) and the Ne'er do wells of sales. You know 9 jobs in 7 year types.
Yes there are flaky companies too, but it doesn't take more than 3 minutes to text or send an email saying no news. I used to tell candidates, call me, I don't want to forget about your candidacy.
Unfortunately, the real lousy ones ruin it for the ones who do a great job.