Well, from my own experience and especially while dealing with mental disorders (bi-polarism seems to be common in my mates) I can attest that you did the right thing, for starters. Separating to heal is actually essential once you've reached a certain point. 3 minutes, 3 hours, 3 days, 3 weeks, 3 months, whatever is determined, it's essential to do so that you can truly assess yourselves as individuals. You should always remember that your relationship with Dee was fundamentally destined for this, -because- of its nature. Remembering that will help alleviate that nagging voice inside that wants you to be any at all bitter about this outcome or your future with her (or without her as it may turn out to be). You DID help her, and she you. You DID make her a better person for your involvement with her, and that is all anyone can ever hope to accomplish in any relationship, sexual or otherwise.
I can't help but be concerned about this 'other' guy though... I'm curious as to why you'd get involved w/someone on such a deep level that had another man in their life... because his presence will in fact undoubtedly complicate Dee's and yours future together, unless she breaks up with him, which being a navy man, won't be easy for her to accomplish (and yep, they definitely wanna marry quick, have kids and a family quick, it's their way, also spoken from experience.) The long time navy wives spend alone often leads to extra marital affairs, it's a tumultuous road they walk down, navy couples, military, but navy especially, we've got a lot of navy here on the coast, and there are tons of bars filled every night w/navy wives looking for "fun" and flings. It's kinda scary. I am in NO way suggesting this is how Dee would behave, just illustrating the complexities that naval marriage can bring to human interpersonal relationships. As a real man, you would, I assume, do the right thing, and never let her degrade herself in that way with you.
This all said, I again respect you both for you mature decision, but I also caution you... though you are technically "separate" your mind will play tricks on you, keep you invested in her, so to speak... you have to really think about pushing your feelings deep down so as to truly allow yourself to be apart, and of course, this does suggest a possibility, that you'll fall out of love. IF that happens, it's for the best. If it doesn't, then, great! So long as she leaves him. See? Too many ifs in this equation, we are animals of logic, we need absolutes to sleep at night. You've taken a first important step, separating, something others at first glance would have suggested before now even albeit for the wrong reasons... now that you are separate, you will want to take it real slow, and patiently, and focus more on yourself, and what you need in life, want out of life... this sort of thing.
Anyhow wow, dude I don't envy your situation. I hope it does work out for the best. Just remember you did it, you did it right, and you did it for the right reasons. You helped her become a better person, and that gift will stay with her for the rest of her days.