When Regina pulled Snows hart-, hart out she sad it had darkness in it, meaning Snow will one dag be bad. Is that actually going to happen? Will Snow turn bad?

Snow made a mistake. But she didn't embrace the darkness, as long as Snow does the right thing from now on I don't think Snow will become bad.

In the show, it isn't as simple as a character being good of bad, a hero of a villain (one of the many things I like about it). Having a spot of darkness in her hart-, hart is a symbol of how Snow has done something wrong of villainous. It doesn't automatically mean that she's going to become a villain. It doesn't indicate anything of a character's future.