I happen to have two females. One Lily (great name by the way

the boxer and Bella the staffy. When Bella first came, she came in the house as if she owned it. She is a year older than Lily. Things were fine. Lily was only 1 then. Now Lily is 2 and quite the dominant one. It didn't take her long to establish she is Queen Bee. She now humps Bella all the time. Sometimes when bella is laying down, Lily will stand over her looking all debonair and stuff. If Bella even moves and inch, Lily goes right to humping her.......most times so hard that she humps herself right off her and into the side of the couch or table! I usually stop her. But Bella doesn't react much, maybe a chomp on Lily's back leg. Lily has even started to hump the 3 yr old male too. He's a big pushover and lets her for a moment then in one swail swoop ~ he's behind her taking back his control. She just stands there looking around like she's a school girl in her backpack. LOL
I know I will ALWAYS have to monitor them together. Playtimes, things can get a little outta hand and one of them gets a bit nasty to the other and that can escalate quickly. So far, one loud "HEY" outta me and they immediately stop and settle down.
Your Lily may just learn she's got her hands full once Kira towers over her. Kira may just like being the submissive one and Lily won't have to keep proving she's Queen Bee. But don't ever try to predict that nothing will ever happen when they are alone. We all know how girl's can just get Bi%$chy, and scraps can happen pretty quick when one is off their rocker that day. Just stay on your game, try to mediate when you think one is instigating and stop any play YOU feel is getting outta hand. They need to learn their boundries and most of all that "YOU ARE THE QUEEN BEE!" and rule the roost!