I think in replacement of the marriage certificate you might need to take some proof of intention of marriage. Like Maybe ring receipts or venue or something like that. My wife had to prove in the cfo interview our relationship was genuine. I'm not totally sure re the fiancee route but the owness is to prove the relationship is genuine.
Regarding police clearance I think your fiancee should know where to get it. My wife got hers in cebu so a different place. She will need to declare the reason for police clearance is to get cfo certificate. There should be a local office that people go to to get it.