Virtually, everything.
1) the LSU player engages Gabby's leg at a high waist height or slightly lower with one arm underneath it (slightly out of frame) and then the other arm is laid over top as it is brought up to chest high.
2) the leg lowers and then is raised higher again by the LSU player to chest height.
3) the LSU player then further lifts the leg as she folds the knee and tosses Gabby away as she turns into the play facing downcourt thus increasing the energy with which Gabby was thrown. In other words she put her body into the toss.
4) at any point all the LSU player needed to do was drop her right arm downward from underneath releasing it and Gabby's leg would have followed it free to the floor instead she applies significant energy lifting and tossing.
5) there is even more detail to be seen.
http://www.the-boneyard.com/threads/gabbyslam.85068/