Yea the first three I got were females too, I was starting to wonder the same thing lol but the next one was male and I caught him with 1 seal card so it was worth it.
It starts at 1% and only goes up to 2% no matter how low you bring her hp. So I recommend bringing it down until you see a 2% chance and then just start throwing cards. You should be sure to have monsters that can last too, because it could take a while to capture.
I caught my male with only 1 seal card, I also caught a female since they're higher rank than the one I had and it only took 2 for that one. But I was just extremely lucky, some people use over a hundred and don't catch who they want.