One of the reasons for this 2:1 ratio is that male livebearers can be pretty persistent, even when the female is pregnant. There's a reason livebearers are known as the rabbits of the aquarium world. So by having multiple females for a male to bother, then no ONE female gets all the attention and gets stressed out. If you have room you could try adding a couple more females, or getting rid of a male as mentioned. However, I had two males with one female at one time, and the males NEVER went near the female (a little disappointing actually, but thats a whole other story). One thing to do is just keep an eye on her. Watch for signs of stress. You may end up having to rehome someone, whether its some of the males or that female. I had a male molly that was constantly harassed by the other fish. He was so stressed by it that he would wedge himself up behind the box filter. He started to get very skinny and stressed out. So I moved him to another tank where he could be king of the castle. Just keep an eye on her.
Is she a new addition to the tank by chance? Or did you get everyone basically at the same time?