There are legitimate programs that allow something close to this, but the specific scenario you are describing raises a separate question worth addressing directly.
Work release is the most common version of this arrangement. Inmates on work release leave the facility during the day for employment and return at night. It is a real program and it exists at many facilities as a transition step close to the end of a sentence. Weekend-only sentences are also possible in certain low-level cases where the judge determines the offense does not pose a community risk and the person needs to maintain employment or family obligations during the week.
Weekend furloughs, where an inmate goes home for the weekend and returns Monday, are far less common and generally reserved for specific circumstances with significant oversight attached.
Here is the part that matters most in your situation. If your wife is supposed to be coming home and is not showing up when you expect her, or if you believe she has more freedom of movement than she has told you about, that is not primarily an incarceration question. That is a relationship question, and it is a more pressing one.
The straightforward way to get clarity on her actual status and program conditions is to call the facility and ask. They can confirm what type of release program she is on, what her movement permissions are, and what her schedule looks like. That information is available to a spouse through the right channels, and having it puts you on solid ground regardless of what you find out.