Aggresive Female Guppy

Hi, I recently got a female guppy from the pet store. I also have ones that I raised since they were babies(most of them are related to each other, I have 14 at the moment). Now they have their very own babies, and surprisingly, they won't eat them too, that's why I usually leave the baby guppies I can't catch in the main tank with the adults. Now here is the problem, this female guppy that I recently got always tries to eat the baby guppies, which now I have to try and catch all of the babies from the main tank, to the 'baby guppy tank', but not only that, this female always attacks other guppies. Is there anything I should do? Take it back to the pet store, or have it in a separate tank? Or any other ideas? because I was actually hoping it would have babies, since it was so colorful :naughty:.