Why not have the love interest be a journalist for a newspaper, or a reporter at a television station that is doing her own investigating? That way, her and your MC can literally bump into each other, figure out their common goal, as well as falling in love. For an even bigger spin on it, the police officer MC gets into a jam, and his love interest helps get him out, and gets her story in the process?
This is how I wrote it originally in the outline, but as I started to write drafts I thought, well anyone with a youtube channel could go out and get this with today's media technology. However, I do want them to be married from the start though. But let's say she is part of the media. Is a cop going to tell his wife, "oh by the way, I am going to get payback on the villains and use my police powers to do it, wanna come see"... Or I could write it so she follows him without him detecting her doing it, but would she put herself in a dangerous situation like that though without it coming off as foolish. That's the problem I have is how do you make her risk her life, without it coming off as stupid to the reader.