Tom served to Sue, who set up Stacey for a spike. Stacey went up for the spike and hit it into the ground on Team A's side. In the process of spiking the ball, Stacey hit the net with her hand.

Who won the point and why?

Since this is not my area of expertise, I searched Google under the key words "volleyball rules for touching the net" to get these possible sources:

http://www.livestrong.com/article/406444-volleyball-rules-for-touching-the-net/

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.

Based on the scenario you provided, it is not possible to determine who won the point without additional information. The outcome of the point would depend on the rules and regulations of the specific game being played.

Based on the information provided, Team A should win the point. This is because Stacey hit the net with her hand while spiking the ball. According to the rules of volleyball, hitting the net is considered a fault. When a fault occurs, the opposing team is awarded a point.

Not Stacey because you're not supposed to touch the net.