Well, that's an interesting question. Well, that has one answer, but adds more questions. Well, Let's start what Pearl is to Rose. She is more or less a tool. There I said it. Pearl was nothing but a fling for Rose. She served a purpose, got too personal, so, she got rid of her. Pearl was replaceable, as you can see when she had Harold Smiley as her foreman when she abducted Amethyst. Show in the grand sea of Rose's life, Pearl was just like any other. Now, Rose wasn't mad that Amethyst had sex with Steven. She was mad that she took his virginity and he fell in love with her instead. Read Bad Romance again, and although she mentioned that Amethyst fucked her son, notice how she became more focused on the fact that she took his virginity and has him loving her over Rose. She uses words like, "my", or "mine", when she talks about Steven. Amethyst is loyal to him yes, but she isn't as possessive as Rose. She understands that they are equal, and she can't force love onto/from him. She loves him enough to let him make his own decisions.

Rose isn't as willing to let Steven hold on all the reigns.

So to answer your question, she didn't do anything to Pearl, because wasn't worth her notice.

For SHES__GONE love all your questions. They provoke deep thought into why I wrote the way I did.