I am a US size 6 often times, 5'4", 115 lbs, very little in terms of bust (34A), and the M fits me just fine. There would be some room there for a woman with more curves at the top but wider hips than mine (I think I'm something like 37" hips) would cause the elastic to hike its way up to the waist (which would be annoying).

I just followed the measuring chart very precisely. Measured my bust waist and hips, checked out the chart. Says order M, I ordered M. It's a fairly tight pro racing fit indeed... So I'd probably suggest that you order the L size, but just make sure you measure yourself out and check out the sizing chart.

It's a great jersey by the way! I have the short sleeves and I LOVE it.