@OP: I have the feeling you just try to keep on delaying the “moment”.
Believe me, by doing this, you are just putting yourself under torture, whatever she will say and no matter how awkward it might feel, it’s BY FAR better having remorses than regrets.
Now stop thinking how it could go, how you’re gonna ask, what’s the best way to react and all this bullshit where you try to predict how this is gonna be because in the end it will be different…
If I were you, I would not wait for this “dinner” to say it, I would go ASAP to her place (now for example, don’t wait for your pleasure, you know you want it).
Be sincere, don’t make up a speech!
Again, whatever she’ll say, you’ll never look back so :
1) MTFU
2) MTFU
3) go to her place now (if you have the time to read this, you’d better be there at the moment)
4) once said , you’ll be happy to be done with it (plus maybe you’ll have a girlfriend, only bonus here)
you should be heading toward her place now…