Sorry, meant to reply to this yesterday and got sidetracked... 😉
First off, let me say....
Welcome to the forum, and congratulations on making your first post! We're thrilled to have you with us!
Now onto this issue at hand....
An extremely generous offer from her, but I would decline. As you rightly stated, even though it's a generic design, it's a life long commitment. And if she were to pay for it, you'd be forever reminded of her through it. Future gf's (assuming you two eventually grow apart) would likely be jealous and resentful of it, and you may grow to regret it due to it's association with her in the future. Better to let her buy you some other equally expensive gift with sentimental value that can more easily be disposed of or handed off if the situation every comes about. 😎