Generally speaking, try to avoid situations along the lines of, "If you don't roll well, the entire scenario ends right now." At least, at the start of the scenario. As the rulebook says, only call for a dice roll if both success and failure offer interesting possibilities. "You fail, game over" is rarely interesting for anyone involved.
Also, before setting up any kind of conflict, compare the relative skills -- your wife was defending with a 2 against a 4, that's really stacking the deck against her. As a GM, you should be aware of the relative probabilities of rolling a given result, and that something like 80 percent of the time, the result is going to be between -1 and +1.
Keep those numbers in mind so you can properly set things up -- I generally only throw something with an advantage of 2 or more at my players if I want them to have a really hard time of it because chances are, they're going to need to invoke aspects to make up the deficit.
(That said, my super-powerful fae and vampires have a history of rolling like crap...)
By the rules, there's really nothing stopping a character like Dani from doing just that, so the best thing for a PC against her would be to avoid the conflict -- as others suggested, make some concession, invoke aspects, or just come at the situation from such an angle that she can't "attack."
(That said, also be aware of the trappings -- if you're doing an intimidation attack, that would be the Intimidate skill, unless Dani has a stunt; that might even the odds considerably -- Dani has a lot of presence, but maybe when push comes to shove, she can't lay out an off-the-cuff insult very well.)
Not all conflict has to be, or should be, about knocking everyone out. Maybe Dani doesn't just want the PC out at all costs -- maybe she wants to embarrass her long-term, so a "taken out" doesn't mean the PC leaves, it means she stays but it's clear nobody wants her there and she has to deal with that.
The same applies to physical combat -- the goal of every enemy you face doesn't have to be "kill the PCs."
The golden rule here: The GM is not playing against the Players. The GM is facilitating an enjoyable game for the Players.
Personally, I've never used social combat more than a couple times, because frankly social consequences are so removed conceptually in my mind from physical consequences that I don't think they should overlap, and my groups have always preferred just roleplaying it out.
