Technically 'paraphillias', which is what we all have to a certain greater or lesser degree, are indeed currently considered to be a 'treatable psychological condition' under the DMV definitions. Homosexuality used to be classified as such as well but the gays have a far better public lobby than we do so it was reclassified. Some countries now consider paraphillia to not be a disease.

Generally, however, paraphillia is usually only considered a problem from a mental health point of view if it seriously affects your ability to function day to day. So, a sexual fetish involving leather is fine if you keep it behind closed doors. If you start crawling around in public, obsessively sniffing women's shoes it may be an issue. Ditto if it affects your normal performance in sex. If you can still get an erection when the fetish is absent then its not a problem.

What may help in this case is her getting more involved in the lifestyle. She may benefit from reading more on the subject, talking to people who life the lifestyle 24/7 on e-mail or these forums and even meeting some in person. She clearly enjoys the sex side of it but is confused and lacking knowledge in the social aspects. You need to communicate with her more - get her to understand you and the lifestyle. A couple of frank and open chats about it may help. You could also do something where you each write down your sexual fantasies and then swap papers and promise to do at least one from each others list at some point.

The trust issue is a concerning one and that is nothing to do with BDSM. A lot of women have this, however, especially when their man has a hobby which they do not understand and where lots of women do it. The question in thier mind becomes 'why are they with me when they could be shagging one of those women who understands their strange hobby'. This can in some cases translate into 'clearly he is having an affair with one of these women' but since she cannot prove it (because it is not happening, I hope...) her best tactic is to keep you under control and away from women.

By the way, I don't think I have ever met (or been in a relationship with) a woman who didn't try to change their man in some way after the relationship started. This is an extreme case but not uncommon.