I wouldn't say there is no evidence. There is some evidence, for example, from the all-female peacekeeping unit from India that served in Liberia, which said that local women actually found this to be very empowering and that they enjoyed interacting with women. I'm not sure if that's because they were women or because they were simply empathetic and good in the sense that they actually related well to people. Other research says that if you're dealing with someone who is armed, trained and wearing a uniform, you're as likely to notice the uniform as you are to notice any other trait or identity marker about that person, and you're much more likely to notice the uniform before you notice the gender.
I don't think there is enough evidence to show that women are somehow naturally trained to relate better to victims of sexual violence, especially because knowing how to respond to victims of sexual violence is something that requires actual training. That training can just as easily be provided to men, and men can just as easily respond to those challenges.