Adopted a Peagle from the pound how do I handle the aggression?

About two weeks ago I adopted a Pekingese and Beagle mix from the pound. She was very sick and we have nursed her back to health. I adopted to her to have a playmate for my male beagle and she will not stop attacking him whenever he is around. Can anyone please offer some advice on how I can get them to better interact. My beagle does not stand up to her he just runs away and yesterday when I tried to seperate them she then went after me.