If selenite poses risks for spirit attachment because of its affinity for the consciousness of dark beings, can it be reprogrammed to do the opposite, such as driving them away, for example?

This can be done theoretically, but it is not the best idea, and the reason is because of the affinity itself. So it is sort of like assigning the door to fight back against a housebreaker. If the door is weak and this is visibly apparent, and therefore targeted by intruders as the point of least resistance, asking that door to stand strong and fight off the intruders is assuming too much and putting the responsibility on the weakest link to take care of the liability at risk, and this is not a good idea. To stand strong, one needs strong partners and strong defenses and it would be better to look for higher energy to add protection and not start with the weakest ally and expect it to carry the load.