I know everybody is wondering why you question things on Charmed. Like what power Melinda Halliwell has. My personal opinion if anybody cares is that she has her mothers powers. Piper became pregnant with her after Leo became a mortal. And like somebody said in The episode of Season 2 Morality Bites Melinda says to Piper " Don't worry Mommy i won't ever use my powers again I promise". You can rule out premonition. She can't show anybody or call them on command. Telekinisis is a possibilty but since Chris already has it I doubt the Elders would give her the same powers. I know Chris is half Whitelighter but the Elders still have some control over that right? And since she is a Charmed One she would have to have one of those powers. So what does that leave you with Molecular Immobilization. Think about it.