Answer:
First, when your betta has the fry, you must split them up quickly. But in your case, it looks like you didn't separate them. If you didn't, its pretty much hopeless. Just let your betta finish eating the fry. next time though, split them up quickly. Some pet stores usually have nets you can use to move the fry away from their parents.
Unfortunatly, in your case, there really isn't much that you can do at this point. Right after the fry are born, you must separate the fry from its parents. So for now, just let the betta eat the rest of the fry. The next time you consider breeding more bettas, separate the fry from its parents quickly. Most pet stores have betta fry nets so you can scoop the fry away from the mother. i hope this works next time!