If you can't observe Charlie & Gracie all the time
, I would keep them separated
for Charlie's peace of mind and yours! Get her spayed as soon as possible. Have a spray bottle handy and the minute Gracie even looks intently
at Charlie, say "No" and distract her by throwing a toy. If she actually attacks him, immediately spray her, and say "Bad girl!". You want to get across to her that this behavior you
do not want and it displeases you. Does she come to you when you ask her? If not, teach her to come by giving the command and give her a treat...piece of cheese or cat treat. Tell her "good girl!". Once you get her coming freely on command, if she starts staring
at Charlie as if she's going to attack, ask her to come to you, give her a treat or make a big fuss over her. Don't neglect giving attention to Charlie, just do it another time
, out of her sight and hearing in another room. Her hormones are at work here, and having Ollie, even tho he was under a year, most males sexually mature at 8 mos. and she knew it. It really did set her off. Hopefully after she's spayed you can get her settled down, and back to how things were before Ollie threw a monkey wrench into the household. I would keep them separated completely after the spaying, and when she's back to normal and feeling good, get them together little by little. Sometimes it's helpful to sit on the floor and play with them both with one of those feather sticks or a cord.
Curious to know what their relationship was before Ollie. You say she was bossy and Charlie passive...that kind of a relationship works, but were they snuggle buddies, grooming each other? or just played together but slept apart?