The visa being granted is one thing, but the time it takes to get that visa after the interview is another. Admin Processing can sometimes take months or even years. Is she Italian? If she is, and no links to higher fraud countries, and nothing else in her background that might raise a red flag, then hopefully a long AP isn't likely.
I still would never quit a job until I had the visa in hand personally. But it may be different for you it would be ok if she wasn't able to work for a chunk of time - if financially you'd be ok then maybe she could take the risk.
Good luck.