What you do is land the EX spin kick, then when they're in the air, use her leap attack thing (same input as a shoryuken, but with a heavy kick instead of a punch) then hammer the punch button when you catch up to them. Spikes them right back down.
When you string it together, it'll send them from one end of the stage to the other. It's so satisfying, and a great way to show off B)
http://www.youtube.com/watch?v=lNWMTXQZr98
At the end of the combo at 2:43, you can see it, though Dan's crammed against a wall, so you don't really see how far it sends him. A lot easier to pull off than you'd think (EX Spin kick lasts long enough for you to get ready for the next move.)