How does the phrase “envy and pride grew higher and higher in her heart like a weed” from paragraph 8 contribute to the meaning of the story?

In context, the Queen becomes so jealous of Snow White that she cannot stand it..... Snow White's beauty made her physically and mentally sick. All she can think of is removing the competition.

The queen took fright and turned yellow and green with envy. From that hour on whenever she looked at Snow-White her heart turned over inside her body, so great was her hatred for the girl. The envy and pride grew ever greater, like a weed in her heart, until she had no peace day and night.