Changing names

There's no reason to want her to take your last name other than a sense of ownership, as harsh as that may sound - it's a control/dominance thing. What does it change in your life or relationship if her last name isn't changed to yours? You love her as Nguyen now, I don't see why you wouldn't afterwards. If it matters that much to her, don't press the issue, as it really shouldn't be such a big deal to you. I agree with the above suggestion of combining names as a nice compromise, but it's also possible to keep your original names without changing either. I've known friends of my parents who have done just that.