Triathlon bike for women (with short back and long legs)

Hi, I need some advice from you...

I'm planning to buy a triathlon bike sometime this year or next season. Now I use a racing bike, a Marvil road 7000 (I actually think it's norwgian design), which is a men's racing bike, the smalles frame size (48cm). In the fall 2007, that was actually the only racing bike available in my size (and that didn't cost more than 10 000 NOK).

I am not that tall, 160cm, and that's OK, but I have a really short back and long legs. So far I have done shorter Triathlons, but I am planning an Ironman next year and I really think I should use a bike that fits better than the one I use now, because I'll be a much longer time on the road (and then, tri-bikes are so cool...)

My bike is OK now, for shorter rides (until 3hrs). I have attached some aero bars on my bike now, which is great, because I really like the position. But the angles are not right, I can see that in the mirror, and my knees are almost touching the handlebars.

I think maybe a woman-specific triathlon bike would fit better, especially because of the steeper angle of the seatpost/tube, so my knees will get more space. But that sure depends on the geometry of the bike to use.

My question now is: Does anyone here have a women-specific triathlon bike of the smalles size? And how is the top tube, is it really shorter, that is, more women-specific? 

And do you by chance also have a very short back? How do you manage that? 

Here in Norway we don't have that many bike stores and choices, especially not for women-specific tri-bikes. So it's really difficult to try a bike before buying.

I thought of a Scott Contessa Plasma, or a Trek Equinox WSD, since those branches are available in Norway, and I cannot afford a very expensive bike (and don't need one).

Please share your experiences with me! 

Thank you