Audio problem: When Fletcher gives Max his birthday gift, the shot changes as Fletcher starts to say, "I hope it's not partially digested." When Fletcher's face comes into that shot, you can see that his lips aren't moving.
Audio problem: When Fletcher is trying to settle the case his client yells at him saying things like "I'm the victim here". In the behind shot of her head you can see that her lips don't match what she's saying.
Audio problem: When Fletcher is on the stretcher talking to his wife and son, when the camera is behind him, his mouth is not in sync with what he's saying. (01:16:25)
Answer: First of all, she's not "on the hook" anyway...this is a divorce proceeding, not a criminal trial. And second, this film has multiple inaccuracies in its depiction of the legalities involved (see Legal Eagle's two-part analysis on YouTube for a very good rundown); the fact that no-one brings up fraud is the least of them. It's not important to the plot, so it is simply brushed aside, counting on us (the audience) not worrying too much about it, like so many other lapses of reality in comedy movies.