Angelfish may be able to help, however they'll probs make a meal outta the neons when you're not looking. Female bettas go crazy over guppy fry, alot more then what the males do, so I've found.
Though, you should just get rid of them all completely by the sounds of it. How many adult females you have anyways?
If you decide to get rid of most and keep only one sex, females and males are pretty close in colouration, but the females live longer apparently.