Hi! Well, it is fairly normal for friends (especially female friends) or family of the female submissive/slave to be concerned about the potential for abuse. They might fear you getting hurt, killed, or taken advantage of. I agree that it is surprising for her to say essentially "he's no good", when you've already been together for so long, however a good relationship can go bad at any time and that is how she is perceiving this.
Your desires are not "wrong", "weird" or even all that uncommon. The truth is, from what I have observed, most people have some fantasies within the bdsm realm. Whether or not they act on them, is another story. The bottom line is, are you being true to yourself? Is this what you and you alone want for yourself?-- Not him, not your friend or anyone else. Oak is correct- you may lose some vanilla friends, and even family members over this. It's imperative that you are being true to yourself, regardless of what that truth is.
Regarding your friend, IF she were talking to a person in a vanilla relationship, where one party was suddenly very controlling, her advice would be on the mark... if not a little too tame of a reaction. What you need to do is try to educate her about bdsm, and the 24/7 lifestyle in particular. If she knows little or nothing about it, or "knows what she's seen on tv", she is viewing this as you setting yourself up to be abused. Hopefully, with some real knowlege she won't be so apt to over-react. Best of luck-- Jenn