I agree with all of the above. Since you have had them in the same tank now for some time try removing the smaller festae for a 2-4 weeks and re-introduce, or divide them. IME dividing or removing fish has been very successful for me in pairing and breeding. In fact I've been growing out 10-12 together in same tank for about 6 months also. They're all 3-4.5" now, in actually thinking about taking the 9 largest and doing 3-way dividers in three 6' tanks. This IME has worked to allow the sub and dominant fish grow faster, healthier and gives them more confidence in which I achieve pairs faster. And this way its not as hard for me to switch around males and females with each other to see which one likes which better.
Either way good luck with yours, and you may have to allow your male to outgrow the female before she excepts him