And you would know what an inexperienced fighter would be? Inexperienced can mean a lot of things, but inexperienced =/= afraid, which is what Pyrrha is. Any inexperienced fighter could either run away like a coward or blindly rush in like an idiot, or many other things. Pyrrha's falls into the clumsy, "I need to protect myself but please don't hurt me" child trope. Seeing as she's not some seasoned warrior like her mother, aunt, or her brother (who demonstrates a lot of traditional grappling), "anything goes" for her. If jumping and crushing your opponent or losing balance and letting them fall on your blade works, it works.