Since you're paying for everything (and let's assume your economy checks out; you'll need to provide your own bank statements, etc), the main remaining thing she needs to demonstrate is that she has a good reason to go back home after the visit, rather than stay in Schengenland and look for a job there.
There is no hard requirement for how one can demonstrate that, except that it needs to convince the consular officer wro processes the visa application.
If she's unemployed and has no particular obligations that demands her return (such as ongoing studies), then it's quite possible that she in fact doesn't have the necessary ties to her home country, in which case there's nothing you can do to document them. A Verpflichtungserklärung might conceivably help a borderline application to fall on the "yes" side of the line now an then, but it won't make up for a complete absence of documentable ties to her home country.
A "NOC" is, as far as I understand, a generic Indian English euphemism for a permit (from somebody to do something), and that seems to be wholly irrelevant here. She doesn't need anyone's permission to go; she needs to have a reason to come back.