Welcome Nufutz
Would she consider reading this forum with you? Perhaps if she gets some information it might defuse her fear.
Now, I'm going to take a giant step back and say: Swinging isn't for everyone.
If your wife is dead set against it, the worst thing you can do is PUSH.
Try putting yourself in her place for a minute: many spouses find the idea of swinging scary and threatening. You're suggesting sharing something you two have never shared with anyone. It also challenges our ideas of fidelity in marriage, and it's vital you two are on the same page.
I suggest you read the posts about 'getting the wife to swing' and take what the 'elder' members have to say to heart.
I'm a relative newbie here, but I hope what I have to say is helpful.
Your marriage is the most important consideration.