Sounds like more of an infrastructure design problem than gender related.
Overall data for cycling accident injuries and deaths are difficult to parse for trends like this, but NHTSA, NCBI and other data consistently indicate males are more likely than females to be injured and killed in cycling accidents.
I can speculate a few reasons why females might be more vulnerable to certain types of cycling injuries and deaths, but without better data it's impossible to verify. A sample hypthesis: Women's heads are comparable to men's in size and weight but they generally have less neck strength. This may leave them more vulnerable to head blows and injuries in falls. Now the challenge is to get the necessary data and study it to confirm or disprove that theory.
Another hypothesis: Chicago Divvy bike riders are mostly women who don't wear helmets. (I'm speculating based on observing casual city rental bike riders in my hometown, Fort Worth -- and my observations may be flawed or biased because of the route on which I see mostly young women riding city bikes while not wearing helmets.) Again, we'd need the data to determine whether this is true and relevant.
It's all just guesswork without data, statistically significant sampling and proper studies.