Spreaking from personal experience...Don't recommend/suggest/or in any other way voice your preference of what she should get. Explain the options and let it go at that. She's going to get mad, but it really has to be her decision. If she wants to start with something small...say a little 250 or something, let her. If she's drawn to something that completely turns your stomach and you hate the sight it, let her get it anyway.
I have to say that, feminism aside, I'm a little intimidated by Dan's riding experience and let that and his recommendations influence what I chose as my first bike. It was ultimately my decision, but I allowed myself to be influenced by wanting to "keep up" with him. It was unrealistic for me to think that my measly little MFS course would give me the ability to keep up with some who had been riding for, well...lots of years.
She may have to work her way up to a 600 or 750. She may want to start with a little Honda 250...or even <gasp> a scooter! If she gets something that she isn't comfortable on, she isn't going to ride. You may think it's a waste of money to buy a bike now then another one in a year or two as she gets more accomplished as a rider. But remember, if you buy something she isn't comfortable on, you're going to have a bike in your garage gathering dust and she'll never want to ride.
I have always been drawn to Vespas, but for my first bike, I let myself be influenced into a Bandit 1200....waaaaaaaaay too big for me - too tall, too powerful, too everything. I dropped is about 3 times then never got on it again. Then moved to a V-star 650...better but still very heavy. Again, it sat in the garage gathering dust. Finally, last summer, I got a Vespa 250GTS. I love it. I ride the 50 mile round trip to work as often as I can. It's been through the Dragon - twice. Hellbender a couple times and the full stretch of the Cherahala.
When we got back from the Eureka Springs MNG last month, I felt it was time for me to try a little sporty. Over the past 3 weeks, I've ridden Dan's R6 almost 10 times and I'm getting more and more comfortable on it. To the point that I've taken over riding the '6 and he had to go get something new to go with the Busa.
Remember, I doubt that anyone here got on a Busa or GSXR750 the very first time they rode. Think back, but I'm betting it was a little dirt bike that you all learned the basics on.