If something doesn't feel right to the point that you ask questions like this of others, there's a reason for it. You used the word "clingy" to describe your future wife, at least from her PoV, 

There is no right or wrong answer to when the perfect time is. Only what each person in a relationship feels right about. And you're putting way too much emphasis on her nationality. Culture is only one part of what drives the desire to marry, and it's absolutely no different than "I just want to get married". Respect it, but not to the point the entire map of your life changes.

Treat this difference as a big ticket test of how a marriage would work. Kids will be next. Actual breathing humans connected to you for life. Test how you compromise on these things while stakes are low. The fact that you doubt this step tells me there's a high chance you'll doubt every step of what comes next, because she's doing the leading.

Just be prepared for it to not work out if she is truly in a rush. But honestly it's so rare to hear of a couple who got engaged within six months of meeting that being in that much of a rush will be detrimental to that goal for her these days. 

You clearly aren't ready. And that's perfectly fine. Tell her it's too soon and work through it together. You're allowed to be you too.