How indicative is a terrible HR interview of the company’s quality?

Having someone in the role is a good indicator of the company. HR are usually good go to people for many things outside of the IT field.

I've been doing HR for 17 years. Many times I have had to ad lib an interview. I wear many hats but I do not do every position nor do I pretend to. My standard questions typically outline the applicants information. Believe it or not, some people lie on their CV/resume.

Job descriptions are often written off of ones that exist online that are curtailed to the company but my job description is not all inclusive of what I am recruiting.

The fact that there is a physical person in an HR capacity should make you feel more excited about the company. A lot of companies opt to use PEOs and recruiting agencies. Having someone in the role is a good indicator of the company. HR are usually good go to people for many things outside of the IT field. Your previous experience may be different because every company operates differently so you assuming she knows nothing about IT seems to imply you know everything about it which I would find incredible..

The fact tthat you had the opportunity to meet someone after her is also a decent indicator. My role as HR is to filter applicants. Sometimes 100s of them. I don't memorize information and about each application and I've often forwarded resumes to managers to help go through so she might not have read yours.

There's also quick fill positions that don't have full job descriptions.

There might be a correlation between company quality and HR but I think it's opposite of what you're assuming. I might be partial but I'm pretty sure I know what HR is about.