Parentheses or colon inside em-dashes?

Should I use a colon, parentheses, or none of them to introduce the word "Arabic" in the following sentence?

I am passionate about languages —including my native one: Arabic— and a fan of accuracy and perfectionism.

The other option would be:

I am passionate about languages —including my native one (Arabic)— and a fan of accuracy and perfectionism.

but Word doesn't agree to this one. It corrects it to have a space between the parentheses and the second em-dash.

The problem is that, except in certain contexts, the colon is interpreted to be (almost) as "strong" as a "full stop" (period), both in terms of the spoken-language timing/emphasis, and in terms of syntactic analysis. Em-dash, on the other hand, is a hair mushier, but is allowed to take the place of a comma in certain syntactic structures.

Placing a colon "inside" paired em-dashes (or inside any other parenthetic form) is confusing at best and goes against normal conventions.

Thus, your second option is the better one (and let MS Word go to ... somewhere -- it's screwed up writing ever since it pushed out WordPerfect).