I think it works out well that they're covering for each other. If what I've read is truly, she attacked him on some level, and he was driving under the influence of prescription painkillers. So they both have an interest in keeping away from the cops.
Domestic violence accusations are always a big deal.
People wouldn't let it go if it was a husband (celeb or not) accused of hitting a woman with a golf club. Even if she was hit because she "didn't keep it in her pants."
Their attempt to cover this up won't make this all go away so easily. Hello, Tiger Woods...welcome to life as a celebrity.