Hi again. It's not that she can be charged for something that she never did because they suspect that she did it. The police weren't there when it happened, so it comes down to evidence. If the evidence shows, beyond a reasonable doubt, that she drove while under the influence, then she will be prosecuted. It's like if you heard a scream outside your home followed by gun shot, so you run out to see what happened, and you find ***** *****ks holding a smoking gun pointed at someone lying dead on the ground with a gunshot wound--it's certainly possible that someone shot the victim, forced the gun into ***** *****ks' hand, and fled in the moment between when you heard the shot and stepped outside, but what does the evidence show?
Regardless, the police only need to find that there's probable cause to suspect that a crime occurred to make an arrest -- the case won't be prosecuted unless the district attorney's office believes that the proof against her is beyond a reasonable doubt. The fact that your wife wasn't in the driver's seat and the car wasn't on is significant, but it's not clear on what the other evidence against her might be. So, if she has not yet been summoned to court, she can't yet know with certainty that she's going to be charged. If she is charged, she and her attorney will be able to see all of the evidence against her, consider the evidence in her favor, and only then estimate whether it will actually end in a conviction. If she can't afford an attorney, one may be assigned to her when she first arrives at court.
I'm never going to tell someone to not get an attorney in a criminal matter. That said, if it was my wife, sister, or mother in her situation, I would probably advise them to wait to see if charges are actually filed before telling her to get an attorney for a first-time DUI. Every situation is different, so she needs to do what is most comfortable for her, but it's normally not that urgent.
As for jail time, for a first-time DUI and "obstruction" charge, if there's no bodily injury or property damage, and if the driver is age 21 or older, there's normally not any jail time whatsoever unless the person's Blood Alcohol Content was 0.20 or higher -- 2.5 times higher than what is needed to be under the influence. If the driver was "sloshed", jail time is more likely, usually around 10 days in custody.
Let me know if further clarification is needed, and please feel free to leave a rating once you are finished. (It doesn't cost anything extra to do so and it is the only way that I may be credited for my answers.) Thank you!