When people are so similar I imagine its much easier for the passion to fizzle out quickly and eventually view eachother as siblings...

Differences keep the fire going I say. I don't mean you should have nothing in common but it really seems like there's no challenge in this relationship whatsoever. You said it yourself, it's perfect. Well it was until the passion died.

Doesn't seem like you disagree about much if anything pertinent, so when did you 2 have the opportunity to learn how to argue passionately (and fairly), have epic make up sexathons and then find a compromise???

I'm not saying arguing is fun, but its fundamental for growth in relationships.

There's a reason why opposites attract, and I've never seen it more clearly than in reading your post.

If you 2 decide to stay together, please remember that just because you like all the same things that they shouldn't all have to be done as a couple.

People even or rather especially couples, should have individual interests / activities. Smothering eachother also kills that flame pretty quickly... Fires need oxygen afterall

Also falling out of love is inevetible. Nobody's honeymoon phase lasts forever. I have fallen in and out of love with my bf time and time again over the years. Thats just part and parcel of a longterm relationship / marriage. Don't let it discourage you.

As long as the love is there, falling inlove can be achieved multiple times. I personally think its the stupidest thing ever when people break up / divorce because they fell out of love, its a problem with a very simple solution. But I guess most people believe that the "inlove" feeling is a permanent fixture and testament to the quality of their relationship, when infact its love at its core that is fundamental for a relationship to work. Not the butterflies and racing hearts. Although it certainly is worth the effort to keep both hearts afluttering

Try changing things up a little, romance her again, but not in the obviously predictable (and possibly boring) way she would expect and see from a mile a way (because you 2 are so alike) surprize her do something out of character...

Lastly; If she needs space, give it to her, maybe missing you is just what she needs to make her want to jump your bones.