Sounds like the infamous female-female competition building up. Rough play can easily escalate into a serious fight. Do not leave the two together unsupervised. There are several threads on this topic if you type it in the search button. Consider hiring a trainer to come to your home and determine the best plan of action. But interview several to make sure you like their philosophies.
PS: buying two of the same toys will not solve things. They always want what the other has.
D, adolescence big time
"If love could have saved you, you would have lived forever." RIP my awesome Wolfie Dog