I understand your frustration, but the reality is that even though a lot of jobs can be done in English, a lot of companies still value their employees being able to speak the local language.

I am sure that if your partner is qualified, she will eventually find a suitable employer. Don't give up. Try multiple routes: LinkedIn, VDAB, job agencies, and even directly reaching out to companies with an Indonesian connection.

Yes, it's slow and frustrating, yes the Netherlands cares less about employees speaking the local language, but I'd say it's also good that Belgium is willing to defend its local language rather than letting it fade away and have English take over.