When we talk about the best dancers in Hollywood history, the conversation generally centers around Fred Astaire and Gene Kelly. What you don’t hear mentioned nearly enough are their partners—the women who danced with them. That’s obviously a mistake. Nearly all the great Hollywood musical dance numbers of the 1930s, ‘40s, and ‘50s include women. Granted, they were not dancing lead most of the time, but that doesn’t make anything they did any easier or less remarkable. In fact….