Re: Im Sick!
Here's what ya do: get her a good, thick pair of denim jeans, find a leather jacket that fits her (if yours does - great) and a helmet. Take her, the bike, and the above stuff to an empty and/or abandoned parking lot - and show her how to ride.
One of two things will happen: 1) she can't stand the contraption and may never understand what you see in it, in which case you're no worse off. 2) She gets hooked and will want her own, which is the more expensive route but at least she won't be able to feel justified about griping at you.
I think my wife secretly wonders what it's like. She's seen what I'm turning that ancient JC Higgins into. She looked at it longer than she looks at most of my creations. In the end she said it was "Very pretty, very retro." I think I could get her on it.
Then, what could she say?
"There is nothing wrong with wanting a motorbike that is an extension of your personal taste and fashion sense; if you must ride somewhere, I say do it with style