Verbal vs. Written Job Offers

What happens when you get a verbal job offer, you verbally accept over, request confirmation of the offer in writing to formalize things, then hear NOTHING back from the employer? I know Mark & Mike remind us all that until you have an offer, you've got nothing, but my wife recently interviewed for a role at a reputable university, and was given a verbal offer (role, title, salary) on the spot, immediately after her interview. What's happened since is rather bizarre. 

They extended the verbal offer on a Thursday, requested she give her decision by the following Monday over the phone, which she did. Everyone seemed excited, and the next step were for my wife to resign from her role to get the ball rolling on the transition. Naturally, she requested they first provide her with some sort of a written confirmation of her offer to formally capture the offer & acceptace BEFORE she resigned, and they employer's gone quiet. She wrote an email to the 2 hiring mangers 10 days ago requesting a formal offer in writing prior to resigning. No response whatsoever. So she sent a follow-up 48 hours ago, and still no response. She's informed them that she wanted to talk to her manager this week, so they know the urgency. 

To make things even more peculiar, the hiring manager is already CCing my wife on team emails now, which seems really sloppy because she hasn't even formally accepted in writing and she clearly wouldn't want the word to get out until she officially resigns. 

What could be going on here? I've never heard of anything like this happening. Is it possible they changed their minds? My feeling is that this doesn't signal great things. At best, the employer is quite sloppy with their hiring, which doesn't say great things about how my she might be treated once she's actually an employee there.