I rode my Grandads 100cc Yamaha for a year while I saved up for a real bike. It was a loooong year, but I made it to the end and bought a Triumph 750 Bonny. Rode that for a couple of years and then bought my brand new 1981 Harley Wide Glide. Yee Ha!
I've got a 1990 Harley FXR now. It doesn't look like an FXR anymore. I love Harleys.
So, the point of the story is : Buy a smallish, used Jap thing and get used to riding, then move on up the scale.

Silly aussies. ;)

astrahl, take a long look at the Yamaha V-Star 650. It's got a very low seat, which will make it easier for shorter legs to balance at a stop, and it's a great looking bike with lots of features for the money.
The shaft drive is nice, it requires less maintenance than a chain.

You may also want to check out http://www.ridemyown.com for motorcycle reviews from a woman's perspective.

The VStar 650 is what Yamaha started making after it stopped making the Virago line. The 650 is virtually identical to the Virago 535 (except for a little more horsepower).