But for the "initial interview" she conducts with all incoming patients to gather information for a diagnostic. I haven't found any candidates that fit her needs. I'm thinking of building a small tool with her tailor-made questions easy to use and maintain.

Across the different projects I've worked for, I've seen lots of basic CRUD/form web apps being built with different stacks and general-purpose frameworks, but all ended up being hard to maintain and bloated in features. Maybe Django forms were the exception to that rule. I also took a look at https://www.reddit.com/r/selfhosted/comments/8ghoy1/looking_for_self_hosted_form_builders and tried a few of the options outlined there but none convinced me.

Do you guys know some modern and OSS form-builder I can use for this?

TL;DR: I'm looking for something like MS Access but modern, self-hosted and -hopefully- better looking to build custom forms, store and consume results.