because she never became a citizen- you don't recieve citizenship just by being married.
you have to apply for citizenship. maybe she felt more alliegence to her home country.
And it takes awhile even if you're married. So she may have tried but if there was a break up and she's no longer married her application would be halted.
As to motive, it certainly does not need to be financial. As we've seen on here year after year, people kill their loved ones for a variety of unfathomable reasons- rage, jealousy, to prevent a break up, to save face, etc.
The story about her ex finally giving in and giving her the cat after she threatened him and then installing an alarm system immediately after, should ring alarm bells in all of us when considering that her fiancé is missing and she's been charged with murder. Sounds like she could be a person who loses it when "pushed". And frankly, not from any place of logic, something in her face chills me. She looks sinister to me.
As as to a "faked" death scenario, first of all, there is not one hint that Viafore had any trouble of any kind. Second, there is just no possible way on earth, IMO, that someone is going to continue with the plan when arrested and charged with second degree murder.
We often come up with elaborate what if scenarios in these cases and I have yet to ever see one remotely pan out. The most likely scenario is almost always what happened. Here, it is that this woman did indeed purposefully kill her mate as thousands of murderous people do in ill-fated relationships, for one reason or another, every year.