A few years ago I have spoken with an agent who helps with government servant looking for government loans, he said and I quote "no, the current commitments held under private banks will not affect the government servants' application for their own government housing loan scheme. The latter relies solely on their grades and income levels"

I always tell my clients to apply for commercial banks first too, to "save" their government loans, as if you apply for government loan first, the commitment will appear in your payslip and it will affect your application, while the reverse is not true.

But I have to put a disclaimer here that I am not involved in any way with government loan application and processing, so I cannot represent them. It would be best if you can have your fiancee to talk to someone in the agency itself.
You are welcome.