Looks like fun
It's fun to watch Nieve learn, and much of this process is mimicking what she observes Ronan doing. One of her more humorous efforts to watch is her attempts to jump. Ronan is an impressive leaper for a three-year-old - both over and off of objects - and I'm sure to Nieve it looks like fun. So she does her best to be like him, trying to become an effective jumper.
Nieve's jumping technique is getting there - she seems to understand that it's important to bend your knees and thrust upwards quickly. She also understands that what makes a jump a jump is getting your feet off of the ground. It's the 'getting air' part that she's working on and has, to her credit, problem-solved in her own way.
Nieve cannot generate enough upward momentum to do a graceful takeoff and landing; instead she pulls her feet up in an effort to get airborne, which results in her plopping down on her backside, sometimes with quite a bit of force. She's prone to do it even on hard surfaces and occasionally ends up rubbing her head due to the jolt. We hope she learns (quickly) that while her approach may give her the 'flying' sensation, it's probably not in her best interest to continue to 'jump' in this fashion.