This is a tough dilema, and although we can all offer you advice on delivering the message face-to-face, you have to do what you feel comfortable with. Because if you decide to deliver message in person and waver in just the least bit, she will be ready to pounce all over you like a Cheetah chasing down a Gazelle!!
We all know that 99% of women can sense the blood & weekness of a man from over 500yds away...They have an evil gift of tasting their prey before they even sink their teeth into it.
If you do decide to deliver this in person, you might want to take Starsky's advice and rehearse this multiple times in front of the mirror or a very trusting friend who could pretend to respond like your W would. Another option would be to take a couple Xanax before you see her & wing it