You've restricted the options, but I'll still share what my initial reactions are.
Firstly, if this has been going on for more than 20 years, it's NEVER going to stop, and discussing it with the instructor is unlikely to change anything in a useful way. If she's willing to put up with it, she needs to just accept there are no certificates and never will be.
If she can't do that, then I can only think of two things that might help, and neither is desirable (apparently):
- Find another instructor. Know that she probably would have to start all over on her progressions if she does this, unless she can find one who teaches very similarly and is willing to have her skip-test to her current rank.
- Deal with the organization. Note that this probably means she's ALSO going to do #1, because I can't see an instructor who pulls this kind of nonsense liking it very much if she goes over his head.
You've not mentioned which art this is, or the country, and I would probably not understand the familial obligations and warrior caste culture anyway. From my point of view, I can't see why a person would accept 20 years of excuses, and keep expecting something to change, nor why they'd stay with that instructor if the certificates matter to them.
(As a note, I've never issued a certificate. I've never personally promoted anyone to black belt, but I'm not sure if I'll issue certificates for that, either. I just don't think they matter very much, except as something to put on the wall and remind us of our accomplishment.)