Feel free to check out DSM IV or V for typical diagnostic criteria. You aren't qualified to diagnose*, but can definitely get a good guess as to whether or not she fits. There's no harm in that.
However, I advise caution. Personality disorders are fairly non-specific. (NPD, for example, has about 30% co-morbidity.) In addition, an autism spectrum disorder + high sensitivity can look an awful lot like, or even be co-morbid with BPD or NPD. (Suspicion of one of our MCs.) Bipolar can look similar too.
If there is uncertainty, then you probably, at most, are looking at traits. Diagnosis is intended for _significant_ impairment. For example, having a meltdown and throwing things occasionally is not _significant_ impairment. Repeated assault and battery on a passive target, followed by threatening the police officers who arrive, may be evidence of significant impairment.
That said, BPD tendencies are more than enough to create significant R/S issues and a perfectly valid reason for divorce. The difference is that, with effort and communication, there's a reasonable expectation that BPD tendencies can be worked around by a rational, flexible, hardworking person.
I am a bit dubious about trying couples counseling with BPDs. Most people report pure failure and recommend separate counseling. My wife and I have had some limited success. (5 counselor's later...most of whom ended up yelling at my wife within a few months.) If you try, I recommend finding a PhD psychologist. I also recommend keeping your expectations strongly limited. The main benefits were:
(a) An awareness in my wife that her behavior was abnormal. (5 MC's later.)
(b) Modest behavioral changes.
(c) Some useful advice applicable to practically any R/S that helped me eliminate issues that were within my power to change. (scheduled dates, et cetera)
I am modestly in favor of MC. However, this is largely because I'm a pessimist and believe that outside documentation of significant behavioral issues is potentially useful in a divorce - particular for custody. Besides, you never know until you try. However, if you try MC, and your spouse spends the first 10 sessions evading responsibility and demanding you make changes until the MC starts yelling, then there is some reason to suspect that MC may be less urgent than focused therapy.
If your spouse has significant BPD tendencies, and assuming you choose to stay (a dubious proposition), you will most likely need to bear most of the burdens in the marriage. (If you can't, you should probably not stay, though there are always exceptions.) You will need to find a balance between adjusting to minimize unnecessary conflict and setting firm limits to safeguard yourself. Boundaries (Townsend) is a decent guide to maintaining those limits. Many books exist on non-violent communication. BPDFamily is an excellent resource. Be a bit careful - if your wife has significant NPD tendencies, BPDFamily's advice may not be ideal. The Wizard of Oz and Other Narcissists isn't bad. Bear in mind that, even if you are doing an excellent job, BPDs will remain difficult to live with.
*If you suspect that a S/O is BPD, by definition, you're unlikely to be rational enough to make a truly unbiased judgement, even ignoring the fact that you're in a R/S. If they actually are BPD, staying indicates that you have some sort of issue - usually codependency or narcissism, although YMMV. If they actually aren't BPD, then crazy people tend to diagnose a lot...