degree's in english and office admin, etc etc, so this allows her a damn good knowledge to copywrite. Some people have degree's in marketing and thus sell themselves as copywriters.
That reminds me of one of the most common qualifications used (not that I'm implying your wife is unqualified in any way, it just reminded me

)
The (in)famous "Degree in Computing Science" qualification. Having an actual degree in something related is certainly a good start, and of course the HR types will, out of desperation, latch onto anything that will indicate some form of outside, third party acknowledgment that you've learned at least *something* related to your job.
Of course, what you learn getting a CS degree is very often really in depth information on things you will probably never need to know in real life - just like most other degrees.
Stupid story - I was the IP/IT manager of a company some time ago. Did all the websites, SEO, presentations, user support etc, etc, etc. In addition to a large portion of their legal work. I spent 10 years in university for the privilege of knowing what I know and frankly it isn't too much - I learned a LOT more on the job dealing with real life issues that never come up in a classroom.
Anyway, I was transferred to a US division and, since I'm a Canuck, had to apply for a US work visa (fair enough - damn foreigners coming in to steal jobs had better be better qualified than the locals...) Since the job required in depth knowledge of patents, offshore finance, website design and network admin it's not like there was a big lineup of qualified candidates.
But I wasn't allowed in unless I could show that I had a 4 year diploma in computer science. Why? uh, we (NIS) don't know anything about what you do so we want you to have a degree in something. I have a dual undergrad BA/BSc and a degree in Law. Nope, not good enough. Um, I've been doing this job for 8 years? Nope, still not qualified.
To make a long story short, due to a combination of a good lawyer and me making a list of everything I've ever done in or around computers since I was a teen, I am now the proud (?) owner of an official declaration by the US NIS that I have a "4 Year Degree in Computing Science, or equivalent thereof".
Yay. Don't know a damn thing more than I did before the declaration, and way more about my job than anyone with an actual CS - as a matter of fact, they would not be qualified to do it. But without it I wouldn't have been allowed in.
This isn't a rant against NIS - they are doing their job the best they can and it's not unreasonable to check stuff. The point though, is that sometimes what is checked isn't your skills, but your paperwork. And the more "official" it is, the better.
At the moment, the "best" certification to start from is a generic CS degree combined with either real life SEO experience or some other SEO type certification.
Many of the best SEO's DO NOT have the CS degree, so I say "best" with some hesitation. Frankly, having a CS degree almost disqualifies you for copywriting

(joke - kind of)
Knowing what I know, I do think it's better to be able to show successful clients, the respect of your peers and current knowledge of the SE situation. But that's hard to measure and many HR depts simply can't/won't do that.
The other option, of course, is to start your own company and then consult - no one asks for the consultant's resume or CV, they just want to know whether they are good at their job

Ian